People come and go. Bad things happen. You get hurt and you cry and for the rest of your life you just regret what happened.
But regretting why you trusted someone or why you did something or what you could have done doesnt really help. They are things that you cannot change. So instead of living with them, take out the best memories and the lessons learnt from it and throw the rest away. Live your life for NOW. Life is beautiful and every moment that you spent crying over what could happen is a waste.
Ofcourse there are things that haunt you forever and make you feel scared. But instead of hiding from it, face your fears. And when its over, the sun will be shine over your head again :)