You get obsessed with a task. And you worry over it. You're like a little monkey. You dream about it. You fantasize. You drive yourself crazy over this little task. You become your own little taskmaster, and it's all you can think about. The world narrows down to one little point, one little task. It's all you can do. Your head and body is flooded with a desire to get to the task. It's kind of a madness, certainly pretty absurd. But you can't help yourself. You are stuck on the task!
UPDATE: And what was the task with which I was obsessed? I have a Tubescreamer guitar effects pedal, it was noisy and not working correctly, so I opened it up and started re-soldering, and re-soldering, and re-soldering. What started out as a device with one problem ended up as a device with many, many, many problems. I became totally obsessed with trying to repair the thing, and basically destroyed it. I should have given it to a monkey. He might have had a better chance of fixing the thing. I ended up trashing it! I am now in the market for a new guitar effects pedal. Some obsessions are not worth pursuing!