I know that what I am about to say will cause controversy for some of you, I hope that you can bear with me.
Regret seems to me something that most people live with as a way of either inspiring them to do better, punish themselves for mistakes they have made or just an uncontrolled emotion that comes and goes as it pleases.
For me though I can't say that it is any of those things, although I understand the concept in theory of regret I can say that I don't have any. Not one! Sure there are things in life that I wouldn't have mind skipping or having done different, but I don't regret it.
See I believe we learn from each thing that happens to us so if I were to regret the things that have happened would be the same to me as discarding the lessons I have learned. I am who I am because of the mistakes I have made and learned from to better myself.
When life hands you lemons make lemonade. So why regret? Learn and go on!