***MAKE MISTAKES*** - LOTS of them and regularly. Now's the time. If you're not, you are playing it safe too often and likely won't amount to much but the cookie-cutter self for your demographic. (The worst mistake of all. Will bring regrets in droves later - look around ;) You'll never make such flavorful, interesting, painful, stupid or instructive mistakes when you grow older. Don't change a thing! Especially if you love someone, love them without a hair of difference from how they are, especially if you care for them. Same goes for you (while not discounting everything else in this section!!)
Don't waste so much time thinking! Go do things! Make those mistakes already! Don't waste so much time on stupid things and worse, stupid people! Waste your time constructively - learn something new, take a walk and think, meet new people, do something - don't just stew in your own juices all day!
Be alone constructively. Don't be alone with just your fears and the cudgel of your guilt all the time. Be alone for good reasons - to reflect on all parts of your life, to write (and write often - the best therapy!), to cook and experiment in the kitchen (so you can invite friends an dates), to plan, to learn. Use the time wisely, PLEASE!
An iron faith and unreasonable optimism will get you through the toughest times. True friends and ones, with all their rough edges, will help a great deal, as well. Choose them wisely!
Don't be intimidated by very successful or famous people - they're just as human, with the same foibles. Don't lionize them. Learn how they overcame their human problems and character flaws to get where they are today.
Don't wear your complex(es) on your sleeve or face! Everyone can read you much more easily than you think.
You can fool some of the people all of time and all of the people sometimes. but you can't fool all of the people all of the time.
Don't be ashamed of yourself or anyone close to you. It's a poor reflection on you, much more than them.
When you're angry, ashamed or annoyed by someone, you're usually projecting some problem of your own. Have enough presence of mind to realize this and work to correct the problem in you.
Don't criticize someone unless you have basis for it, have taken care of your own shit first, it's strictly necessary to correct a problem and it's for the good of that person or the enterprise or humanity. If you criticize, don't cretin-ize.
-- Look for patterns in everything. How does your GF/BF behave? How does your boss behave at certain times of the day, week, month, quarter? What do they have going on outside work that's bothering them? How can you help make their life easier?
How does the job market function? Are more jobs posted after quarter-end results are in? After the Fed announces interest rate policy?
Look for data on anything you need to understand. Try to see the patterns in the data. It's a gold mine. Not all data is on a spreadsheet - the best is in your brain.
Observe people, observe trends in politics, finance, psychology, history. Form your own opinions, run them by people, argue your case, lose, improve.
Iterate. A-B test yourself constantly. Refine, repeat. Induce, deduce, repeat.
Automate your life and thought processes even while expanding and learning new things. It will just make the process easier and more efficient. At least make an effort and do your best. Otherwise, you'll just get hopelessly lost.
Learn to integrate knowledge and information effectively. Organize ruthlessly - into folders, compartments, niches, etc. Make sense of what you observe.
Once you start seeing patterns, you can contribute a great deal more than others who work thoughtlessly. You can improve processes and create and invent based on this process of pattern-seeking.
Creativity is a critical (but of course not only) component to your individual success.