Beginning writers like drafting, but they hate revising. Surprisingly, experienced writers hate drafting and enjoy revising. That's because they know how to get good revisions. Here are the main points that they know. Don't work on-screen, print out.
Computers make drafting easier, but they make revision much harder.
They do this in two ways. First, computers don't know how to write, but they know how to fix the small stuff. As a result, the minute a piece is all written, and if it's still on the screen, the most reasonable next step seems like checking spelling and punctuation. Second, it's harder to read words from a screen than from paper. Thus your eye gets lazy and doesn't look closely enough to catch minor errors.