How do explain to my parents that I don't want my life to be about PROVING myself?

so I'm 21 years old and I just started college. I'm doing it for the learning experience. I'm not sure what I want my career to be so I'm just focusing on learning and enjoying myself. but my parents are taking my life to the extreme. I've never ever said that I want to be perfect but they criticize my every single move. I just want to live my life!! I don't want to live for them. I want to live for myself. but even if i have an off day they will treat it like its a catastrophe!!