A - The task requirements and goals might not be clear enough. If you are trying to get yourself to “plan for a project” or “write a book” then it’s hard to identify the next actionable items. Put some time aside to figure out what physical things you can do to move the project forward. Try break down the larger tasks into the smallest pieces possible. The goal of the project might need identifying, or the requirements fleshed out from a supervisor.

B - The task might exceed your current competency. Sometimes we know what we have to do, but don’t know how to do it, and then we become avoidant rather than admitting this. In this case, it’s worth figuring out what you do know how to do and what you don’t know how to do, and be honest with that. Then slowly ask for help or read up on the things you don’t know.

C - The tasks might really not be worth it. Sometimes you are assigned tasks that don’t actually help you achieve your long-term goals, and so your brain demotivate you from doing them. Maybe the payoff is low, maybe you don’t learn anything new from them, or maybe a colleague you don’t like will gain credit for the tasks, or maybe you just wont be rewarded or appreciated for getting the tasks done.

There is a single advice I would give to anyone writing software, and specially to great devs : Always optimize your code for your most junior developers. I agree that it is not a very popular advice, but it is the one that, in my experience, give the biggest bang for the buck.