For me, you can view that problem two ways, "I'm going to work harder and prove my value to the company" or the move the goalposts approach, "I really didn't want that promotion anyway, I'll spend more time with my kids! No one will judge me as a failure if I do that."
Shifting priorities can be rational if you honestly realize your tastes and interests have changed over time, but most often it seems shifting priorties are just a manifestation of weakness - a decision to flee rather than fight.