Live in the moment. You can't change the past, but obsessing over it can ruin your future. Not to suggest you have been doing so, believe me I understand your frustrations.
I am an atheist to the very end, but there is great wisdom to be found in this:
The only thing you can control is how you treat yourself and how you treat others. The way others treat you is something you have zero control over - so try not to drive yourself crazy trying to "fix" them. Treat others right, and if they don't treat you right, let them know and establish space.
How I wish I could take my own advice...