Give yourself credit, I bet you have learned a ton in your life. It is never too late to mentor others with similar struggles as yourself. Don't beat yourself up over the past. While you can't change your past or even your present, you can change how you view your life. Instead of beating yourself up over indulging on the not so healthy habits and worrying about the amount of time you have left, realize that you are enjoying the things you like and if you don't like that stuff then work on that. Don't worry about how long you have, make better use of the time you have. Sure bipolar is a lousy illness and for me it really has been like 1 step forward and 5 steps back, and it is frustrating, but it is a different kind of ride and I could definitely do without the valleys, but the peaks are great, but you can't have peaks without valleys. Bipolar disorder has lead to some of the greatest inventions and works of art, and even spirituality in humanity it really is a gift and the best gifts always have a drawback just like the drawback of life is death, of love is loss, of extreme highs is extreme lows.