It's as simple as choosing to be happy. Choose to take advantage of opportunities to learn how to be happy. Choose to be in environments and around people that increase your happiness.
Attitude is the central influence in your life. Everything you do and everything you feel are both decisions and choices that affect your attitude. Happiness depends on your attitude. Do what you enjoy, enjoy what you do, and don't do it for money or glory. Live for the now and don't dwell on what went wrong, what was, or what could have been. If you can't be happy today, what makes you think tomorrow will be different?
Take a step back and re-evaluate your goals. This is your life. You are free to revise and edit as you go. Think positively and have an open mind. Be yourself. Live to be spontaneous, natural, and real. Say what you think and do what you feel. Don't worry what others think about you.
Find meaning and a purpose in life. Find happiness. Choose to be happy.