Richard, my daughter likes to spend her time asking questions of a philosophical nature. Not too long ago was the dreaded question, "What would you go back and change in your life, if anything?". I told her I would get back to her after I had given the question the time and thought that was warranted. I came to the conclusion that, if you are happy and content with yourself and the ones in your life at present, there should be no reason to change anything in your life. The good, and bad, experiences make you who you are. If you had not lived your life in exactly the same manner, you would not have the life you have today. One seemingly insignificant decision you made 20 years ago, say such as deciding not to go into one particular restaurant that night, where you ended up meeting your spouse, would alter the course of your life completely. Every single step in your life has led you to the here and now. Now, if you are not happy with your life, yourself and the ones in it, that is another story completely. Dan's philosophy comes in quite handy at this point, should this be the case.
I think a quote by Alexander Graham Bell simplifies my thought process much more eloquently. "When one door closes, another opens; but we often look so long and so regretfully upon the closed door that we do not see the one which has opened for us."
That being said, if the source of your regret is the hurt you have caused another human being, in my opinion, that cannot simply be let go and chalked up to life experience. Apology is the only noble avenue to pursue, not so much for you, but for those you have aggrieved. In this case, you apologize to do what is right, not necessarily what is easy. If they accept your apology, so much the better for both of you. If not, see the Webmaster's coping mechanism.