Well, I guess I regret not being braver. I ended up changing my major anyway. My biggest regrets are that i screwed around in high school and now i have to pay for it. It may never be to late to try, but it may be to late to do it right. Do yourself a favor and do it right the first time.
Regrets are the things which humans have many of, generally speaking.
I think mine would be that I did not stand up for the person I used to be in my younger days. I did not recognize the uniqueness of me. My mother was the same way and is now, as well. Though we continually grow as the humans we cuttently are, we never outgrow the humans we have been. So, I think my biggest regret is taking 30 years to appreciate me for who I am now and who I was then.