How are you supposed to handle a situation where your boss makes you feel like your not good enough?

My boss makes snide remarks about once a month. I've only been at this job for approx. 3 months. The first remark was the 1st week. As I have started to become older, I have been caring less and less about what people think of me and when he makes these comments, I really just want to tell him where to go and how fast to get there...if you know what I mean. I am doing the very best that I can & I have been told by previous employers that I am very conscientious, I am slowly losing respect for him and I feel as though one day I will really say something I will regret.