I've become a big fan of David Allen's "Getting Things Done" book and website: http://www.davidco.com/
to help me with this very issue. The book he authored has really helped me stay on track and stay motivated with my current goal and/or inspiration, but also helps me capture all of my good thoughts that I would have but then 'forget' by the time I needed them later on. You can easily find a copy cheap online or at a used bookshop. Read it through and take notes and then give it a try for a month or so and see what happens. He teaches you to get the thoughts out of your head and onto paper, and then from paper into specific, smaller steps that you take toward completing your major goal. Sometimes not breaking things down seems so overwhelming and that steals the focus and love we once had for a project. It sounds a bit structured until you try it and I still don't follow it as well as I should, but even some of his most minor tips (and those from other readers on his website forum) have helped me so much...such as planning and consolidating trips to the store in specific steps or going out of town to coordinate with other things, ticklers for important projects, etc. I hope you're not as 'all over the place' as I am
(which makes me lose focus and momentum in no time, as I start a new project continuously, or so it seems), but this is a great aid. And you'll find some really good and supportive people out there (again, check out his site's forum) doing the same thing, too, and having some success in making their goals actually happen.