We are, at this time, a combination of our basic genetic code (which I believe also carries the foundation for our temperament) and our life experiences.
I think that all significant events in our lives change us in one way or another. How much and in what way is up to the individual.
One way we can be changed by a negative event is to learn from it and improve our lot in life based on this knowledge. Another way we can be changed by a negative event is to allow it to negatively impact and change our lives.
I am not one of those people who believes that I need to forgive. Forgiveness is for the benefit of the person doing the forgiving, not the person receiving the forgiveness. Many people are negatively impacted by not forgiving. I happen to not be one of them. If I do not forgive, I am not eaten up by it… it just is.
Now usually I forgive including things even if they are severe. For instance, someone tried to kill me in 2005, doing severe damage to me. He apologized which I did not accept at the time. Instead, I told him that if he went into the military and made a man of himself, I would forgive. He did that and years later I forgave him because he is now not the same person as the one who attacked me which is what I required.
If someone does the same thing repeatedly, asking and receiving forgiveness from me, after a couple of times I do not forgive.