Ask HN: How do you handle (financial) regret?

A while back I quit a startup because I was unhappy with how management handled a number of situations and I didn't see any signs of that changing for the better.

Fast forward a year and the company is thriving, and I realise that I have foregone a massive financial opportunity in terms of compensation.

I think the original decision was fundamentally sound then, but it's very difficult to let go of thinking "what if I had stayed".

I can't imagine I'm the only among HNers that have been in this situation.

How have you managed this internal conflict?