1. Your social skills and work ethic contribute to your success more than anything else (any classes, seminars, beliefs).
Most people are good at a limited range of things (studies, sports, hobbies, side gigs) but ultimately in your 20s, you learn that most successful are those who can manage to work hard while keeping up with wide variety of people.
2. Life is not always as flowery and beautiful as the movies describe them to be.
3. Finding a mentor is worth more than any college degree.
In your 20s, life throws alot of curveballs at you. In between college classes, cooking/laudry, hookups, loans, one can get very lost and that is when a proper mentor can keep your personal, academic and overall progress in check.
4. Money management starts not if you already haven't started saving!
Almost all college students are broke, but that doesn't mean you have to be. Manage your finances very well (eat out less, cut smoking, use student pass/Metro Rail, carpool, share/split costs whenever you can). Additionally, work or get internships in the summers in between college to get extra money and experience.
5. Always be on time.
Being prompt and on time is a must. In your 20s, when assignments, group works, proctored/timed testing, interviews begin to take a tole on you, you must always learn to be on time if not ahead.
6. Always be equipped and prepared.
Being prepared goes hand in hand with being on time. From interview to girlfriend/boyfriend's birthdays being prepared will help you plan better. I have a buddy in college who I met in my first hard business class, who always finished his work and test prep for the Tuesdays and Thursdays section he was assigned for and was able to help out and tutor others in the later sections and make extra money on the side.
7. Break down life into semesters.
If there is any 12+ years of schooling have taught me is that you have got to break down things evenly. There is a reason school/colleges are broken down into: Fall, Spring, Summer, and Winter mini-sessions. In your 20s, when so many priorities are jumping out on to you, coupled with the fact that you not have been mentored properly to handle them, I believe breaking it down is the first step.
8. Make room to recover, you need it!
Your 20s are when most mental and physical stresses and disorders emerge. To combat such drawback and to remain in shape and well, always create room to breathe. Whether it means to create time for bowling with friends, going to bars, going to socials, getting time to self care, or just going to the park to play frisbee with your girlfriend/boyfriend always make room for rest each week and several throughout the month.
9. Learn to Cook a variety.
Cooking is a skill that comes to spotlight in your 20s. Away from the comfort of your home cooked and mom-made meals, you are now left with very few food options. $.75 Ramen noodles anyone?
10. Keep in touch with your family (especially mom)
In your 20s, your social circle drastically shifts. You begin to make new friends, cut out or lose touch with some old friends and solidify your relationship with a few. In time of transition, don't forget to keep in touch with your mother and a few immediate family members who have been there to celebrate most of your successes.