[zechs]

One thing I can say is that it's possible to feel the way you feel even for someone in a situation where they seem like they "have things figured out".

Read Seneca's On the Shortness of Life. It and other works of Stoic philosophy help me at times when I feel this way.

Changing jobs/cities/partners can sometimes be the answer, but finding a source of value that is robust to changing circumstances is the only hope we have in life.