Yes, give yourself deadlines. I work under deadline (real ones, with work) every day and when you MUST be finished by a certain day or time or whatever, then you finish and move on to the next thing. It's easy to get into overworking stuff to death. For me, I have print deadlines, so after a certain date, the comic is at the printer and I cannot mess with stuff anymore. If you are doing this on your own, you could just say, "okay, I have until Friday to finish this" and after that, move onto the next thing. Take the learning experience from that piece and use it on the next one. Keep moving forward. And best of luck.