This is a tough one, just because perspective changes things. Usually, without benefit of experience/perspective, people genuinely do what they think best at the time. Now, we're looking back.
That said, I'm with Michael_Gee with regard to learning to play a musical instrument well. I always liked to sing, and, at one time, was active in the church choir, participated in some performances, and could draw general compliments for my voice. I also was pretty good at playing the piano by ear and my parents paid for piano lessons for me for a while. I'm ashamed to say that I didn't take advantage of them then, though, and although I can still play certain things, and can still read (basic) music, never practiced enough to become truly good at it. Now, I still give thought, sometimes, to starting to play/take lessons regularly again, on my own. But I don't know if it'll ever really happen at this point.
I also would have given more thought to my career choice, instead of just, pretty much, sticking with what happened to catch me first -- journalism -- during college. Nowadays, I'd advise high school and college-age people to pick a field that, of course, they're interested in and might like, but also that, generally speaking, pays well.
I'm not materialistic, at all, but there's no denying the benefits, in almost every respect, of having more money, and I'd say to make that a major consideration in your choice of career fields. You'll be able to set yourself up better, both for whatever your current life holds, and for the future, and to live much better and more comfortably in your retirement and during your elder years if you have more money. I look back now, and, because I've always been good with my money, I often think if I'd made even, say, $50,000 a year for any length of time at all during my prime working years, I'd probably be close to wealthy and able to do pretty much whatever I might want now and in the future, as opposed to having to save constantly, and pick and choose what I'm going to do when. The opportunities that money can provide are practically limitless, and you can still be smart and good with money when you have it. Especially if you have it. (The stories of lottery winners who end up broke and miserable drive me crazy for the idiots that they must be to lose/blow it all. It's just inconceivable to me).