How do i stop being hard on myself?

I am a sensitive person and if someone criticises me I can get upset (not crying just upset). People say you should be yourself. I do act like myself but I always look like a tool. Even after all the advice people give me I just don't have the confidence to not care what other people think. I often thought that some peopl like you and others won't but at my corridor at university all the guys everyone is laughing with and likes them, yet they just seem to only accept me and I appear happy. Even when I try to be funny people just seem to think I'm being stupid.