I just had an extremely simple but promising theory of why work is aversive!

Work is the stuff you tell yourself to do. But sometimes you tell yourself to do it and you don't, because you're too tired, engaged with something else (like playing a computer game), etc. This creates cognitive dissonance, which associates unpleasantness with the thought of work. (In the same way cognitive dissonance causes you to avoid your belief's real weak points, it causes you to avoid work.) Ugh fields accumulate.

The solution? Only tell yourself to work when you're actually going to work, with minimal cognitive dissonance.

Autofocus helps accomplish this by helping you avoid telling yourself to work when you're not actually going to work, which means cognitive dissonance doesn't accumulate.

Designated work times, etc. might also help solve this problem.