Oftentimes as a freelance writer you find yourself juggling multiple pieces at once. This can really cause a lot of confusion, especially if your topics blend into one another. Currently I'm working on three major pieces, all dealing with the legal industry and each having to do in some way with litigation. The deadlines are days apart.
Some freelancers probably work on one piece until completion until working on the next. Others flip back and forth from one assignment to another seamlessly. I take a mixed approach. When writing, I make sure to finish a first draft of one piece before beginning another. However, while writing on piece, I can still review notes and create an outline for my next piece. Whichever piece is due first is almost always the first piece I tackle, though if deadlines are no more than a day or two apart, I might weigh it by which assignment is more work intensive.
What it comes down to is knowing your work ethic. If you are a great multi-tasker, than by all means take on as many assignments at once as you can. But if you are a more linear worker, than you might have to really work hard to complete multiple assignments on time. Devise a method that works for you and stick with it. Take some time periodically to scrutinize your method and see if there are improvements can be made. Freelancing is all about efficiency, and the most efficient process will yield the best results.