From the Reddit miracle:
Thinking about the past is one of the easiest ways to bring yourself down, because it is always the horrible stuff we remember the most (stupid brain). I used to work part time in a kindergarten, and one of the most valuable lessons I found was the total bliss and lust for life that small children have. THAT is what I taught my clients; To take back their lust for life, not by forcing themselves to live up to other role models, but to look forward to their own adventure... You are your own master, and you can walk down any road you like!
Ask yourself: "What keeps me from doing exactly what I want to?" The most likely answer is: "Myself."
What you have done in the past will only hurt you if you do it again. Make sure to tell yourself what you will never do again, and then tell yourself what you WILL do. Form your resolve, but base it upon your own courage and independence. Be honest with both yourself and those you love.
Don't try to live up to others, but make your own adventure. Regret is only good for telling yourself what you will never do again. Once you know which things you will never do again, regret turns into wisdom, and wisdom builds character.