Past is something we can't change but we have the present to make our future wonderful.
Embrace the present and live life to its fullest each day. It all starts when we let go of the past and understand that some things are not under our control. And a few years later, we would look back and realize that there is a good reason for every event that has occured in our past.
The only thing we need to carry forward are the lessons from the past and leave the rest. There is so much to look forward to that even our lifetime isn't sufficient for us to discover all.
Personally, I feel that being positive is the only way to lead one's life. Whenever, there is something negative going on in my head I immediately think of anything positive. Doing something for others will really help us build our self esteem. There is so much happiness in making someone smile or bringing a change in somebody's life. And, good set of friends make your life much easier. If you could confide in them during tough times then that is one of your support system.
So, start today and see the difference you can make to your own life :-)