Visit your doctor regularly. A great place to start is with your health. Yearly dental and general check-ups go a long way in preventative health care. In order to be at your best emotionally, you'll need to start taking care of yourself physically.
Surround yourself with people who want the best for you. Ditch anyone who is jealous, insincere, consistently doling out a rude comment or chronically unhappy themselves and trying to bring you down.
Keep other people's problems where they belong: In THEIR life. It isn't your problem that a family member has an addiction. Do what you can to help, but realize it is not your problem to fix.
Participate in your hobby regularly. Find time for the things you enjoy and treat yourself once in awhile to something that makes you feel good.
Put the people you love being around first in your life. Making your loved ones the number one priority in your life will reward you with healthy, fulfilling relationships.
Listen to others. Stop talking and focus on what is being said. If you are busy being defensive all the time, you'll never look inward to make the necessary changes needed to have deep relationships.
Always keep improving and educating yourself. Willingly read self-help books, take relevant classes and keep thinking of things that will enhance your life. Then just do it!