I'm 31 and the one thing I wish I knew was the utter and complete lack of limitations on you as a younger person. Crazy, right? Let me make a metaphor.
Imagine boxing (or MMA if you prefer). Life is like that. Your entire life, you train and train to get ready for your fight in life. You learn the basics. You learn the proper way to throw a punch, dodge, etc. Then you're let out to compete!
But there's a trick no one tells you about. Once you hit 18, you can sign up for any fight you want. Any weight class, any rules, any thing at all.
Now, that said, you have to be able to compete at that level, or else people will be far less likely to ever take you seriously again... But yeah. You can really do ANYTHING. Especially those first few years. Because after that? You'll probably have debt. And then you're fucked until you're about 50.
Had I been more aware of this, I'd have finished a novel far before now (as I've currently not). I'd have printed my own comics, too (I've not). I was a dumb (average) kid, in that I bought into "the way things are done", having been raised that way. I spent far too many years of my life and too much money, trying to do things the way I was taught they were done.
I regret so much, and I never realized it until I hit my late 20s. Eventually it got through my skull that there is rarely a "one way" to do anything worth doing. Just be as capable as possible, and do as well as you can. Most people? They're pretty eager to help.
But remember, those basics are important. You have to know your craft. You won't knock out the champ on a hope and a prayer.
There are a lot of people that will try to take advantage of you, don't make long term commitments like bank loans, they will put pressure on you, try to avoid it, live your life.
Having good education helps you better understand the problems that you will confront, combined with knowing how to analyze them to make a good decision is the most important thing to know and also do stuff that you are passionate about, don't push yourself doing something you don't like because someone else wants to.
I'm nearly 50 and from my experience this isn't BS. I have no idea whether the OP speaks from experience, but the advice itself is worth keeping in mind.
I should also add that applying such advice is difficult, but just beginning the process sets you apart from the vast majority. You have to make an attempt to understand the shades and nuances, and that requires talking to those with experience and/or reading some really good books over and over until you've soaked it all in.
The key is to seek versatility in core areas. If you want to be a programmer (or a musician, or anything else), by all means go for it. BUT you still have to figure out what successfully managing your finances and relationships, etc. entails - just don't be guided by loose advice from family and friends or even "experts". Do your own homework, set your goals, even as you pursue your passion. The sooner you understand the pitfalls of debt, risk management, and perhaps even the notion of passive income, the sooner in your life you will be able to make more time to pursue your passion, your pleasures and the relationships that form the far bigger part of a meaningful life.
In my case I began my move to get things in order in my mid-thirties. Most of my productive years prior to that were spent pursuing my passion then, golf (and nope, I was never PGA material even in my dreams, so be careful of your passions as well) ... but luckily I caught myself in time. :)
I'm 30 and I spend a lot of my time trying to drum most of this list into my 24 year old brother so it's not far off the mark.
The problem with self help advice like this is that you have to arrive at these conclusions through your own experiences and only then does it make sense (through hindsight).
Saying that, I think the most important point is #11, you want to accumulate as many experiences as deeply and as fully as possible. That's what sets you apart from the status quo and the average. Everything else on that list follows from that as you get older.
As the adage goes, you never regret the things you do, only the things you don't do.
I'm well over 19, there is good stuff here, in fact pretty much all of it is good advice.
If I was to add to it I would replace (8), which is somewhat superficial, and suggest working on your people skills. People affect your life in every imaginable way, all the time, learn how to detect (and manage) the idiots and how to look after those you care about.
