If you change one thing in your life - what would most effectively improve your quality of life?

Get "Dress For Success" by John Molloy. He has a lot of advice for students, and it has no resemblance to guidance you get from school counselors:
1. Vocal skill will affect your earning power more than any other single detail.
2. Acting skill will get you a job offer even if you are not qualified for the job.
3. The most important thing you get from your college years is your address book.
4. The main difference between a successful man and a very successful man is the latter knows hundreds more people, and he knows them quite well.