I have one project that came to mind immediately when I read your comment, so I feel like I know what you mean. A fix turned out to be "tell a friend I want to do X, and ask her to remind + encourage me when the appropriate chance comes up." But social-commitment-type things don't always apply.

I have more experience with projects that started becoming aversive, and that pushed me harder (both emotionally and otherwise) to tweak my approach, which in the end led to renewed focus and progress. Having those examples available helps motivate me in situations where I don't otherwise want to attend to operations long enough to change them from their default. Could the same be true for you? That's the only general suggestion I have.