Have you ever looked into a body of water and looked at a reflection of yourself?
What made us who we are is something that is hard to explain. No, we weren't just made up of good experiences, some experiences were bad, but they also helped make us who we are today. Learning that not all experiences are going to be good will help make you a better person.
If we cannot forget the bad experiences, they are going to impact us for the rest of our lives. What people need to do is realize that a bad experience happened and let it go. No, it may not be totally forgotten, but at least saying it happened, and I am not going to let it negatively impact the rest of my life is important. Being able to accept it happened but not dwell on it will make you a better person. Another important thing is learning from the negative experience and trying not to repeat that same experience.
Looking into who you are is something we all do from time to time, and it's important to look at the good experiences and be happy with them. The experiences that weren't, so good are lessons that we learned and things that cannot be changed, but experiences that we don't want to repeat.
Knowing how to accept that a bad experience happened and letting it go will help make that reflection of yourself even better. You will know that you are a stronger person for letting it go.