**ALL INPUTS DETERMINE THE OUTPUT. Be careful what you watch, listen to, eat, smell and touch. You'll see the results. No, but really, be very mindful of what words are in your muscle,, for example. Words create a reality at beyond what you realize. Hoes, money, cars? Ghetto forever.Yesterday, life was such an easy game to play? Depression, nostalgia? My cat puked, so like, OMG? You get the idea. BE. VERY. MINDFUL.
What are you eating? Why do you put such awful crap in your mouth? You are what you eat and drink, quite seriously. ***LOOK OUT FOR THE HEALTH SECTION OF THIS BLOG FOR MORE DETAILS***
Watch what you say. Always. Just don't say stupid shit that makes no difference in the world or that no one actually hears. Write it down instead, at least. You'll make sense of it later. Say only things that are helpful, positive or at least constructive. Otherwise, small talk is an important art. Know a little about everything - especially local sports teams - to be able to relate to just about anyone. VERY USEFUL.
Watch what you read - again, words are incredibly powerful and create a reality in your head far beyond what you know. Don't be obsessed with news - it'll mess you up and depress you. Read good fiction (classics are best), read on your favorite subject areas, explore new areas of interest.
Be very selective about what your eyes see - movies, videos, people, freaks, gore, suspense, spectacles. It affects your mind more than all the other senses, especially if you're a guy. The database you build - especially of beautiful things - will heavily determine your aesthetic sensibility, whom you find attractive, whom you marry, what friends you seek out, what clothes you buy, how you look, etc. Critical to develop a selective visual taste. Seek beauty, but don't expect to find it easily in all things. Minimize the amount of crap you see and put up with visually (and otherwise).
**BE VERY SELECTIVE and DISCRIMINATE. Have good taste in all things - friends, women, books, co-workers, jobs, food, sex, spirituality, etc. Compensate for your precociously good taste by milking student tickets, freebies, deals, barter, whatever. LIVE WITHIN YOUR MEANS, NEVERTHELESS. Get a taste for what's good in all these areas of life and grow into them slowly.
Don't spend money you don't have to impress people that are boors and/or above your social class. They won't be real friends in the end, anyway, and won't appreciate you or your outsized generosity.
TAKE RISKS and often, but not stupid or reckless risks (ok, maybe a few here and there). Take calculated or at least intelligent risks!
FEAR - "We have nothing to fear but fear itself." (FDR) Fear is a lack of faith, but of course a normal reaction. Fear is dispelled by taking risks (see above) and by strengthening your faith in G-d.
Working memory - develop it!! Memorize numbers, quotes, poems, whatever it takes. Read Jonathan Safran Foer on this subject - how to improve it.
No regrets, EVER. Only lessons learned and applied effectively.