How does one deal with the anxiety and self criticism?

How does one deal with the anxiety and self criticism? Hey everyone! I'm (23 M) a person who's had a mild stutter in school, but never really cared about it and was confident. However, once I got into high school (around the age of 16 in my country), I was very overwhelmed by the competitive engineering exams that one prepares for in my country. I started underperforming here and this had really increased by anxiety levels back then. And since then, I have always been a person who's been anxious. There was a constant comparison every weekend among the students of my high school to determine who stood where, and this further exacerbated my anxious and critical mindset. Since then, my stutter became worse significantly. Even in college, I have been an anxious person and never really seemed to get the right mindset to be confident. People who have faced similar situations in their life and managed to get back their confidence, what suggestions would you give that can help me to just get back to the confident mindset I had in my school as a kid? Thanks in advance!