Here is a sample of the edited manuscript you would receive. (FYI: The manuscript here is the very first story I was paid for. If you happen to be an editor on the lookout for new work, I'd like to point out that it is not representative of my current writing.)
I'm starting this journal because I believe that something bad may happen to me during the course of my experiments, and I want the world to be aware of the strange events that have been occurring lately. My assistants have orders to release this to the press, along with a copy of all the technical information, if I should die before I'm done. It started a week ago, when I first began to see that there might be some chance of success for my project. Time travel. They all said it was impossible, but I have discovered a way to do it. I simply have to build the actual machine now. The problem is that someone doesn't want me to. I have no idea who this person is, although I have very little doubt that it is a jealous colleague who feels I am not worthy of the great fame I will undoubtedly receive for my great discovery. A few hours after I came up with the equation that worked, I discovered a very shocking addition to my laboratory. It was a dead body. [This is a bit underwhelming. Try an exclamation point instead of a period.] The words you must stop now for God's sake were carved into its chest in a desperate-looking scrawl. A note attached to the body instructed me that hereafter, every day I continued to attempt to make time travel a reality, a person would be killed. At first, I took this extremely badly, as may be expected. First of all, here is a dead man in my lab. He was apparently killed for the sole purpose of stopping me from discovering time travel. I believe I would have stopped right away if not for the result of the police investigation. I reported the body to the police and it was identified. A few hours later, the dead man was found to be quite alive and living in a prosperous part of the city. It was soon discovered that the body was also gone. The police decided, as did I, that it was part of some elaborate and cruel joke. The body was probably stolen from a local morgue or a fresh grave. The only problem was how it happened to be enough like a living man to have been identified as him. But that problem could wait. I had more important things to do. Since then there have been two more attempts to dissuade me. One was an extremely convincing videotape of a man who looked exactly like me (and claiming, in fact, to be me) who begged me to stop my experiments and warned me of some horrible result if I didn't. He was so convincing that I was almost tempted to believe him, despite his outrageous claims. The second attempt was a long, rambling note with approximately the same message as the videotape. It's not going to stop me now.
March 30
It happened again. Whoever is doing this is persistent. This time it was only a letter, not even as adamant as the last one. It was signed with the initials as my own. I'm not sure if the initials are coincidence or if this person is still trying to make me believe that he's me. Anyway, my experiments are coming along very well. It won't be more than a couple of weeks now.
April 1
What an April Fools Day this has been. [This could be another good place for an exclamation point.] I got a very unfunny joke played on me. I know now that it must be one of my very own assistants that is trying to stop me. Both of my assistants and I left the lab for a lunch break today. The lab was locked the whole time and only my assistants and I have keys. When I got back there was a plain white envelope on my desk. My name was on the front, written in what appeared to be red ink. Based on what was inside, [I really wanted to see the word "however" here.] I doubt that it was. Inside the envelope were a note and a folded picture. I put the picture aside to read the note first. [I have trouble imagining a person pointing this out in their diary.] It was another attempt to stop me. Whoever wrote the note said it was written in my wife's blood. I didn't believe it at first but the picture was of my wife in our tub with her head split open [Do you mean her throat?] and her wrists slit. I ran inside [I assume you mean "into the house" from his lab. It might be better to say that. I pictured his lab in the basement.], expecting the worst and screaming her name. She was, of course, sitting in the dining room having her own lunch. Of course [These two uses of "of course" so close together sound awkward.], she became very worried by the way I was acting. She even suggested I might want to take a short break from my experiments. It took a lot of talking to calm her down again. I am now determined to stop this insane attack on my project. Though I can hardly afford it, I will have both of my assistants followed by a private detective firm. I would prefer to fire them, but it would be better if they don't know I suspect them.
April 7
Neither of my assistants has been caught acting strangely but it doesn't matter now. I fired them. I am on the eve of my greatest discovery and I can finish by myself. Tomorrow will be the biggest day of my life.
April 8
I had a strange dream last night. In my dream I came from the future and begged myself not to go on. The dream me babbled [add "about"] my first attempt at time travel opening a huge rift in the space-time continuum. He attacked me when I said I wouldn't stop. It was a very vivid dream, obviously brought on by the several attempts to halt my greatest project. I must have fallen out of bed in the middle of it, for I woke up on the floor with a black eye on the right side. I seem to remember the future me also having on [change "on" to "one"] in my dream. Funny how dreams can be so vivid. But this won't daunt me. That space-time continuum rip might be great for Star Trek reruns, but it couldn't happen in real life. I am about to make th [change "th" to "the"] first time jump in human history.
(later)
Something dreadful has happened. How could I be so foolish? My attempt at time travel caused some kind of space-time hole. [Unless the scientest is meant to be incredibly dense, he really should acknowledge here that what happened was just what he "dreamed" about the night before.] Our world is leaking into another one, and the creatures I saw there are not very friendly looking. But I can fix what I've done. I'll simply go back in time and tell myself to stop. Yes, that is what I must do. I'll do it when I'd be asleep so it will seem like a dream. That should take some of the time paradox effect away. It won't erase the effect completely, though. I can feel it already, making all of my memories from before the attempted time jump disappear. I can't even understand the journal I had been keeping. I wrote it myself, but it all looks like gibberish when I try to read it. [I'd like a little more information about how this "time paradox effect" manifests itself, and maybe some clarification that he knows the effect is caused by his intentended action of jumping into his own past.] I know what I did wrong. My machine will work now. Here goes the first jump.
(later)
My God! Am I really such a stupid man? My past self wouldn't believe me about the mistake. He babbled something about it not working this time. I don't believe I could be that stupid!
My wife hates me (rightfully so, perhaps). She threatened to kill me. Part of me want [Change "want" to "wants"] to just let her. God knows I deserve it. But if I'm killed who's to warn the me of the past of my horrible mistake? I am the only one who can run the damned machine.
(later)
I am almost ready to kill my past self, and damn the resulting time paradoxes! It can't be worse than the things I see going on outside. I tried to leave two letters for my past self and even went as far as sending a videotape of myself telling him he must stop. The past me won't listen. What a fool I was! I must be more drastic.
April 9
I've had a few hours of sleep and it has done me good. I know what I have to do now. It's so simple. My wife says I'm crazy. I know I'm not. What is one man's life (a stranger's yet) compared to the world? My wife says nothing is worth that and it won't do any good because if it worked I would have stopped before and this wouldn't have happened. She doesn't know anything about time travel. I'm worried about her. She might try to stop me.
(later)
The stupid woman! My wife tried to keep me from leaving. We fought and she cracked her head against the seat in the entryway. I'm going to leave her as another attempt to stop him. I will place her after one of my already failed attempts, hoping it will shock him into action. He must see how much he'll have to pay! [I'm disappointed to see the wife exit the story so suddenly. I was just starting to get behind her as a character.]
(later)
I am again astounded by my own stupidity! I showed him my dead wife's body to work [Is "to work" supposed to be here? It doesn't make sense.] and even placed a corpse a week earlier. Nothing gets through to him! I can't understand why not. Could I ever have considered my research more important than a life? But I will outlast him. Taking others' lives now is almost a mercy, compared to what the demons from the other world will do to them. I told him I mean to kill one person every day and I mean it. Tomorrow I'll just have to try again.
(later)
I just realized what I've done. How could I have become such a monster? I've been killing innocent people in an attempt to stop myself. What is one man's life compared to the future of the world, I thought. But I killed the wrong man. I must simply go back and kill my past self before I finish the machine. I have so much contempt for myself now, I may die smiling as I choke the life from my past self and destroy the chance for me to exist now. But it will have to wait. I'm so tired. I must do it, but I need to sleep first. I'm so tired.
April 10
I've run out of time! The world is over! The other-worldly creatures have broken into my lab and destroyed the machine. There is no hope. For what it's worth, I am so SORRY!!!
OVERALL THOUGHTS:
This is a science fiction story that's been told pretty often before. That will make it a hard sell in a lot of markets. The story is still enjoyable, though. There's something endlessly fascinating about watching someone descend into madness. This might be a good fit for a pulp market where some cheesiness is forgiven in a good story.
The device of the "time paradox effect" was a bit murky, as I noted above. How did it work? What caused it? Was there a rhyme and reason for what he couldn't remember as opposed to what he could, or was it seemingly random? It definitely needs more clarification for this story to work in a sci-fi market.
I noticed quite a lot of short, factual sentences, like: "It happened again. Whoever is doing this is persistent." It is perhaps appropriate for a scientist to write like this, but a lot of these simple sentences can have a deadening effect on the story. These kinds of sentences were more prevalent in the first part of the story but there were quite a few in the second part as well.
The ending is very bad. It is too abrupt, as if you just ran out of words and stopped writing. Did the narrator really need to get some shut-eye at that point? How lucky for the invading monsters that they managed to destroy the scientist's machine just before he used it to stopped them. The rest of the story shows some good imagination. Bring some more of it to bear and make the ending at least as good as the rest of the story. It should really be one of the high points, if not the strongest moment in the whole story.
This story still needs work before it is really ready to submit, but it does have promise. Keep working on it.