You need to define what 'done' means. I try to create some sort of nice image in my head about how it would be if my project is ready. Then I try to recall thi

You need to define what 'done' means. I try to create some sort of nice image in my head about how it would be if my project is ready. Then I try to recall this image if I see myself tripping off the path. Just to remember myself why I am doing something helps me a lot. I usually write down the core features. I only allow myself to code something that is not on the list if I earned it by working on something on that list the same day. Perhaps you should take a look into some parts of the XP (extreme programming) philosophy. One idea is that you work in iterations and that every iteration should produce something usable. In theory you could stop at any point and should have something 'finished'. In theory...