You can be the type of writer who constantly changes and modifies the same story until, well, forever. In that case this post will have no benefit for you and you can skip it (I won't be offended, promise).
But for those of you who are in this to eventually get published and have progressed enough to realize manuscripts have to be completed, you realize it's going to happen.
Eventually your draft will be as complete as possible. Your beta readers will still be in disagreement over plot, character, and word choice...but they'll catch no more technical errors. You, yourself, have gone through and can only change a word choice here or there. The title page is complete, formatted, and has your correct email address (not the personal one that starts with hotmama12).
Still excited, you put together the cover/query letter and paste it into your email. The excitement starts to turn to manic psychosis about here...You double, triple, million times check it for errors or weird sentences. You attach the manuscript, remove it and reattach to make sure you've got the right file. Remove it, change the name of the file to something you feel is more professional. Reattach. Remove and reattach to ensure you have the right file.
This can take anywhere from 1 to 5 hours.
Then with nervous, sweaty brow and your heart about to explode....you hit send.
At this point, you completely freak out. Going straight to your sent file, you reopen to check for errors, file mistake, anything. You sit for the next 1 to 3 days hitting the refresh button, waiting for the confirmation and acknowledgement response. Often throughout this phase you log out and then back in...just in case the refresh feature is broken.
Once you receive the acknowledgement the little crazy writer inside of you needs a mental jacket. You spend the next 90 days (yes, most responses take 90 days) obsessed with your email and your submission tracker.
Now, the little realistic writer inside of you tries to tell the crazy writer to calm down. But we all know what telling someone to calm down does. Eventually the realistic writer does manage to tie up and muffle the little crazy writer and gets to work on writing, editing, or outlining the next story...but it takes a while.
Usually by this time, within a few days, you get the response from the editor and it's time to start all over again either with the same story or another completed story. The good news is the more times you've done this, the faster and easier it is for the little realistic writer to take control and the more productive you'll be during the waiting torture phase. It really does just take practice and a built up resistance to the neurotic tendencies.
Good writing all!