I have come through this, you sound like you are in a similar position to me.

One thing that helped for me was, imagine yourself 5 or even 10 years in the past, looking at a person in your position. What would that version of you think of the current you? If it is something like "when I have what that guy has, then I'll be happy", examine why your level for "happiness" has changed over that time.

Also stoic philosophy is great, the wisdom of 2500 years helps.