As weird as it sound this is the most free time of your life, on top of the fact that for the most part you remain largely a sponge. In high school, and even part of college you can get away with a lot before it's time to "grow up" as they say. I think the thing I regret most was that I stopped looking for the things I loved to do when I was younger. I remember when I was much younger I tried all sorts of sports, athletics, club activities, etc. and somewhere along the line I get meshed in with all of the stuff you talked about high school being about. It's very easy to be overwhelmed by the sheer amount of things to do as a teenager, but for the love of God do not stop looking. I think the thing I remain to this day proudest about was that time I grew an afro. It was honestly the most freeing feeling (even though after a while the work necessary to keep it neat was excessive hahaha).