While I'm leery to be yet another book recommender in a discussion thread, suggesting a possible non-solution, I have to say Overcoming Anticipatory Anxiety by

While I'm leery to be yet another book recommender in a discussion thread, suggesting a possible non-solution, I have to say Overcoming Anticipatory Anxiety by Seif and Winston is a decent self-help book when it comes to dealing with the core emotional motivators that lead to procrastination and other avoidant behaviors. It's steeped in CBT practices, which I'm not even sure I buy, but I found the "wise mind" concept of moving past one's current anxieties instead of engaging and getting stuck doom-debating with oneself. It's definitely got its share of dubious-sounding supposed anecdotes from the practitioners' sessions, neuroscience that sounds okay I guess, and too much time spent dissecting the problem into different categories. But! the book doesn't repeat itself too much, and it is only about 165 pages, which is practically pamphlet-sized compared to all of the bloated self-help books pretending to be novels or even textbooks. I think it's less of a book with a specific solution than a book with possible solutions that doesn't take that long to read through and choose.