Why does the past have to matter?

I am speaking of our personal past. I don't see why our past must decide who we are 또는 who we will become. Yes, if 당신 will let if a troubled (for the lack of a better word) past can bring 당신 pain in the future but it might not. What I am trying to say is, why does it matter? Why do people decide what kind of person 당신 are 또는 what kind of person 당신 are going to be from what 당신 did YEARS ago? Forgive and forget, right? I mean, I am different than I was but no one sees, they only see who I was not who I am. I had a neighbor that use to drink and party till 5am everyday. (I was younger at the time, school and bedtimes) My parents were furious, seeing that they had to get up and go to work in the morning and get my brother and I off to school. Long story shorter, now the neighbor doesn't do it anymore. We are 프렌즈 as neighbors should be but 당신 still have my mother that brings up the past every chance that is presented to her. Why? Why can't we accept that people can change? I know in order for people to change they have to want to 또는 have a reason 또는 both but it is possible.

Well, thank 당신 for 읽기 this far.