hmmm... that's a deep question, hard to choose just ONE thing... if I could change just one thing, I would have been a kinder person all my life, shown more mercy, compassion, and forgiveness.  I can't change the past but I can be a better person for the rest of my life. 

A very good question.  For myself, having perused all the posts here briefly, I have to say, I would want to be more one-pointed in my focus on music, any music, as in making music, not just listening. Active involvement in anything creative, building instruments, playing them. I think it would be a much kinder world if more people were involved in making music. Somehow it just brings us all together. They say youth is wasted on the young. To a large degree I have to agree. Young people have so much potential, but don't know how to use their time wisely, as a rule. Having said this, I still consider myself young, relatively speaking, since I know that if I am lucky some day I will look back and remember how "young" I was now. We all have only one thing... time. That's all we really have. How we use it is important. I would say, I want to try to be more focused. It's so easy to want to relax and put something off for another day. Television, video games, facespace etc. it can be all very addictive. I found for myself, it's only when you don't have any focus, when you don't have a "life", that's when you succumb to these mind-numbing so-called activities. The hardest thing for me to do was to make a decision what I wanted to do with my time. You have to accept the idea that you are limited, that you will not be able to do everything. You have to choose. Now I know, I would choose music. It's the best... Art's cool, too. But for me, maybe just as a hobby!

Love, Tilly