I regret wasn't very outgoing when I was still studying. All that counted for me were my studies. While others made lots of fun, I was a good quiet girl...
I also regret I never learned to play the guitar. My parents forced me to play the piano, guitar was out of the question. I did buy a guitar after I got married, but never got the chance to follow lessons.
Now, here I am, with NO piano to play on, and a guitar I cannot play on