[Kyle]

Life's too short to have regrets kirk. Whatever it is you've done you must have had a reason at the time and you can chose to either accept it or learn from it. Everything has a value to it and that's what makes you the man or woman you are today. Every success, every failure and especially every missed opportunity.
Ruminating on 'what if's' will serve only to entrench the belief that you made a mistake when the only mistake that a person can make is to not come out of it wiser for the experience.