@The Joker006,
You say "what if we could change it to what we really wanted?" The thing is, how would you know what you wanted until after you had lived? Are you suggesting that this second time we go through life we remember the first time? I am not disagreeing entirely. My own theory shares one similar component to your own in the belief that we do relive this life. Or, rather, we exist over and over again. I don't think much changes each time, as babies have no memories of past lives and even if they did when we enter into a language, we have no way of remembering anything beyond what can be described by said language.
While it is nice to think that we can change our mistakes, I also believe there is no point to it. As much as I regret a lot of things, I only regret them because I have been shaped by cultural, spiritual, instinctual influences that tell me what is wrong and what is right. Beyond all of those layers of "meaning", I don't think right and wrong exist and therefore would bare no regrets outside of this earthly existence.
Think about it. But, thanks for the cool thread to inspire the above thought processes.