I just wish I could subscribe to a project for longer than a couple of years.
With over a decade of experience in my field, I can certainly relate but cannot offer any advice.
I'm currently reading the book below to understand more about this (it's a bit too verbose but it's a decent book I recommend).
http://www.amazon.com/Drive-Surprising-Truth-About-Motivates...
I have a very active life outside. I just wish I could subscribe to a project for longer than a couple of years.