Andrea at MiG Writers made a very good point in yesterdays blog. However proud you are of a finished, polished novel you've written, refrain from reading it when you're working on a new first draft.
Makes sense, right? Why read a great piece of your own work when you're just getting the idea of a new one out? Its rough, basic, and not anywhere near the great writing you're capable of. So why taunt yourself with a finished work? It's likely you (and I) would see this fabulous writing and look at the new WIP, and go, "This first one was a fluke, I'm no good." I know I would give up.
But I think this thinking is so obvious, many wouldn't actually think it. Granted, it could be a great motivation to get through the next WIP, but it also has the equal potential to bring you down. Be careful about the decision to reread a finished manuscript of your own writing, and be honest with yourself about the effect it may have on you, and your current work. If the answer is truthful, and you are confident in it, then follow the course you choose.