What do you do to pass the time while waiting for the other people in your group to show up at big music festivals?

How do I tell someone about my self-harm tendencies? I’m 15 years old, and I really want to confide in with someone, but it’s hard for me to open up. I don’t want to tell my parents, as they are the main problem and I do not feel comfortable telling.
What makes someone demand certain qualities in a partner that they don't possess themselves?