To steal an expression from my country's armed forces and manhandle it a bit, editing is weakness leaving the manuscript. It is very tempting to declare that first draft complete when you finish the last sentence. It is painful at times to step back when you're riding that emotional high. But step back, you must, for the sake of your work.
I have a friend who is very good at editing. She understands the importance of this step to our craft. At one point, I was struggling in the editing process on a manuscript. I began to complain about how much non-fun was happening. Then she reminded me that the goal of editing is not fun. It can be fun, but the goal is not to have fun. The goal is to refine your work and prepare it for your audience. It can be hard work. It is tempting to invert Hemingway's wisdom and edit whilst drunk in an attempt to dull the pain of it. (Do not ever, EVER do this. I did it once and the results were horrific.)
It may be apparent that 99% of my blog posts are unedited. It probably is not as professional as I can be but it is in keeping with my casual style. If you look through my serial story, you will find little errors here and there. I know that I have some misspellings littered through my work. And my grammar is not as good as it once was. (One thing that writing 3 or more collegiate level papers a week is good for is keeping your grammar on point. The other thing it is good for is boosting your word count for typing sessions. It is, however, a lot of work and kinda painful.)
I may skip the editing on my blog posts because I just want to get the work out there as quickly as possible, but I don't take that approach with my manuscripts. Blog posts are like what I whip off in a journal or a notebook. The ideas are cobbled together quickly and my focus is more on getting the concepts down before I lose them rather than crafting the best sentence I can. In many ways, this is how I approach rough drafts. After that draft is finished, however, the game changes.
Once you have your ideas down, it becomes time to polish them and make them easier to read. Sometimes this will be difficult. Taking technical writing and turning it into something for the general populace is very hard, especially if there is a lot of specialized language. Other times, it will be easier. Editing a 5 line poem in blank verse takes me about 15 minutes, at most. The common point between both extremes is that the focus of editing is to take what you have written and make it better.
No one has ever written something that was perfect on their first try. If someone is trying to sell you on the idea that your rough draft is perfect, be wary. Especially if they are claiming to be a professional. It takes multiple rounds of editing to smooth out the rough edges of your work and polish it up so that it shines with all its own unique glory. If you have a deadline to worry about, make sure you factor in time for editing. Trust me, you will not regret it. If you don't have a deadline to worry about, take your time and go over your work closely. And when you have reached a point where you feel like you are finished, grab a friend to look it over. It will take a couple rounds of this process to get your work to the best level.
The other half of the editing coin is rewriting. It is a little more fun. If editing is the act of cutting apart your darling and taking parts out, rewriting is act of putting new parts in and putting your darling back together better than before. It is part slasher flick and part mad scientist flick, if you're looking at it in terms of horror movies. But hopefully with a lot less screaming. I'll talk more about the mad scientist element of working on your manuscript in another post.