"Feeling like this means something's wrong with my life"

This is the belief that holds the others up. If you feel a steady dissatisfaction, something must be causing it, and the cause must be out there in the circumstances, because that's what dissatisfaction is for. It's a signal. Pain means something's wrong with the body, and the hum means something's wrong with the life, and the sensible response to a signal is to find the cause and change it.

Sometimes that's right, and chapter 2 said so. But the research on how people's happiness behaves over years suggests it's often not, and the reason is a little uncomfortable. Ed Diener, Richard Lucas and Christie Napa Scollon reviewed the evidence in 2006 and listed what needed revising in the old idea that everyone drifts back to the same neutral level after anything that happens. Two of their revisions matter here. People have different baseline levels, and those levels depend in part on temperament. And those baselines aren't neutral. Most people sit somewhat above the middle most of the time, and where each person sits is partly a fact about them rather than about their circumstances.

Which means the hum might be your level. Not a permanent sentence, the same review says baselines can change, and chapter 8 is about how. But a level, a place your mood returns to that's a bit lower than you'd like and has been for years, across two jobs and three flats and at least one relationship. If that's what it is, then it isn't a signal about the kitchen. It's the weather you carry, and moving doesn't change the weather you carry.

Here's the test I'd use, and it's my suggestion rather than a finding. Ask whether the hum has a shape. A signal about circumstances is specific. It's worse on the days you see the manager and better on the days you don't. It's worse in the flat and lifts when you leave it. It arrived when a particular thing changed and it would end if that thing changed back. A level isn't like that. It's roughly the same in the new place as the old one after the season ends. It was there before the job and it's there in the job. It attaches to whatever's nearest, and when that changes it attaches to what's nearest after that.

If yours has a shape, find the cause and this book will help you change it well. If yours doesn't, then the next thing is being asked to fix something it can't reach, and the rest of the book is about what can.