Where for me, "feels bad" starts at the body getting tensed up and the gut being twisted, and goes up from this to becoming nearly paralyzed and tortured, with higher cognitive functions shutting down and even the simplest incremental action on the task requires forcing my own limbs to move.

It's like the physically painful stress of suddenly having to make a very difficult choice, except it doesn't go away until I finish the task, give up on it, or... just do something else. So it's less of a "I will avoid doing it", and more of the mind giving up under torture.