While I understand on a general basis how I can get stuck, it's really helpful to have a procedure for getting UNstuck. Here's a good one.

DeProcrastination.co: 3 questions to get unstuck and start making progress by Vita Benes and K. M. Michna

the 3 questions that will help you get unstuck and start making progress are:

1. What haven't I done yet?
2. What's stopping me from doing this?
3. What is making me frustrated or discontent?