The only thing I regret about my masters is not taking real analysis beforehand (I took it for funzies after graduating). Even in a program with an applied focus, it would’ve made my life much easier - most of the classes where straightforward with multivariable calc and linear algebra under my belt, but I always felt like I was on the edge of disaster in the theory sequence where you couldn’t avoid proofs and gnarly derivation. My grades were fine, but it felt like a fight for survival.