Mr. Gaiman, do you have any advice to spare for a 21 year old who is absolutely terrified of screwing up her twenties so irreversibly that she won't amount to much of anything? I keep reading that your twenties are "the formative period," and that so much of our lives end up defined by the choices we made in that span, and I feel like I'm already royally fucking it up.
That’s why the twenties are formative. You do things, fuck up, deal with the consequences. That’s what forms you. It’s also how you learn and how you grow and how you change. You aren’t meant to go through your twenties (or indeed through any of your life) with it all figured out. Get out there, do stuff, choose the wrong things, fuck up, fix what you can, don’t hurt people if you can avoid it, be kind, and fuck up better and more interestingly next time.