I've done that a million times. The trick is to have the right goal. Usually you'll have visions of how it will turn out in the end and not even half way through you give up because it seems that vision won't come true. Think of these projects in terms of years, not months. Then break them down into the very smallest possible parts. Im talking about thinks like making an entire day's goal to just write a single function that does something really small like connect to a database or something. That's how I've managed to finish despite having the same issue.