How do I control my reactions and temper today i was at school and some guy in my class says to me?

"hey buddy lay off the steroids" initially i wanted to either cuss him out or punch him but i managed to hold back and said "listen Ive never done that **** and have been working out since i was 13" and people have asked me or made slick comments about this and i am a big guy about 6ft 200 pounds and 20 years old I dont want to do something ill regret any help for the future thanks.