I think it's a case of the more you have, the more you want, and the more you think you need. . I was invalided out of my chosen career in my 40s and have had to accept a much lower rate of pay ever since. I am earning about 2/3 of what I did in 1995, and probably 1/3 of what I would have been earning had I stayed and progressed. But the funny thing is, I feel better off now than I ever did then. The secret of being wealthy is not earning more; it's being satisfied with less. Enjoying what you have, not hankering after what you might have.
When I was looking into retraining, a careers advisor asked me how much I wanted to earn. I said I had no real idea. She suggested "enough for all the things you need, and a few of the things you want". She was bang on there. Wise words.