Traumatic past

Don't you think that everyone should have at least experienced one traumatic event in there past? I know I did. It was 10 years ago I think when the last years I was finishing elementary school. I had gone bike riding with my friends, there were 3 of them I think. And we'd gone across the road outside of my neighborhood. Then it started to rain. One of my friends asked me if I had some money with me. I think she wanted me to treat her I guess. Well, at that time I thought that we were just going to go to ride our bikes, so I didn't bring any. After that, she immediately said that it's time to end the bike riding activity. At first I thought that it was logical for her to end it because hello it was raining, drizzling I think. But a few seconds after she had said that, it struck me like a needle through my hand, she wanted to end it not only because of the rain but also because I didn't have any money with me. This "money incident" happened a couple of times but with different alterations of the situations. However, it was always her who initiated that I should be the one who always treat them and stuff. I know that they weren't as privileged as I was, but still, I always had this thought in my head that when people, and I mean any type of people, engage in what I know as friendship, they don't just hang out or play together because of their materialistic values. That's just mean and sick. People should have this wonderful bond because of the person that they are. Not because of their money per se.
So, all of the bullying events that I had encountered throughout my elementary years was the main reason why I wanted to study psychology. I want to find the answers why a kid my age was being treated like that. And why had my friends behaved in a certain way. Was it because of their own will or something else?
Answers, answers, that's what I need.