Michael Malice at Thought Catalog has one big piece of advice for writers:
Never edit as your write.
Why? Because you will stifle yourself, and prevent yourself from making any progress. Malice reasons: books are read from start to finish, and so you should edit that way as well. Write in chunks, but don't allow yourself to despair when your syntax clanks and your words don't quite make sense. For him, it works, because hey: no one has a great first draft, anyways.
I have to agree with this advice: if I write for two hours every day, and read that work at the end of the day, I will feel that I shouldn't have worked at all. The words don't fit, and I didn't get my point across at all. But I need to just keep writing! The longer I spend editing one section at the beginning, the slower the entire work will progress, the more I will feel discouraged, if I can just write the entire piece, know that it is rough, and then edit it, the whole work will be much more successful.