Why does the next thing never satisfy?

Because satisfaction is the removal of a lack, and removing a lack leaves nothing behind it.

Schopenhauer's picture starts with the will: a blind, aimless striving underlying everything, ourselves included, that wants nothing in particular and never stops. Specific desires are just where it surfaces. Meet one and it does not rest — it relocates, which is why the promotion, the move and the finished project each produce a satisfaction with a startlingly short half-life.

This is the the hedonic treadmill described a century and a half before it was measured. His version is bleaker than the psychology, because he does not treat it as a bias to be corrected. It is what wanting is.

Then comes the part that makes him hard to dismiss. If striving is the problem, its absence should be relief. It is not — it is boredom, which he took as the decisive evidence. A life with nothing to chase does not feel like arrival. It feels empty, and we go looking for the next thing largely to escape it.

The implication for work is uncomfortable and clarifying. Some of your restlessness at your job is not about your job. It would follow you to the better one, and has probably followed you already.