I'm curious how you dealt with your stingy person identity.

Mainly by being able to point out that its purpose has expired. It was really useful being a stingy person in first-year university–I had a lot of time, and limited ability to turn it into money. Being stingy allowed me to not go into debt, at the cost of maybe a bit of happiness–I always felt a bit guilty about i.e. going out to dinner with friends. Once I graduated, the default was to stay stingy, but I can convince my brain to relax on specific items like "go out to dinner with friends" or "travel to lots of places" because, hey, the whole point of being stingy in the first place was to get me through school and to the point when I had a career and savings and could do fun things.