I have a problem with never finishing things that I want to work on. I get enthusiastic about them for a while, but then find something else to work on.

I used to have this problem. In my case I think it boiled down to the planning fallicy. I'd start a project, make a little progress, but only then make an honest estimate of how much effort would be required for a shiny outcome. Meanwhile, other ideas for shiny new projects would occur, and these were unencumbered by realistic (or, in fact, any) planning.

Part of my solution is to go ahead and do some project planning on new ideas. I find the process of (and even the ancicipation of) thinking through new project ideas, expanding them, devising solutions to forseen problems etc immensely pleasureable. By doing a fixed amount of planning I get a hit of that along with a (usually sobering) estimate of what it would take.