Mistakes and forgiving people

I made some bad mistakes in my life that have led to wrong paths or bad situations to erupt in my life. Relationships or friends is what I'm referring too! But god can look upon me and forgive and forget because thats the way the almighty god is. Why can't people see that? Why do we feud over stuff that makes no sense? Why do we tend to go after someone for their past history of things they have done to you? Why do men tend to hold a woman for things she done in her past and why do women do the same? We just don't know how to let go do we? 22 years of my life and still don't get it! People say you can't change because once you done one thing wrong, you'll keep doing others. Well I say hell no. People can change but its on them to wanna change. No one can change you or make into someone you not. I just wanna know wat's ya opinions on this people!