How Can I build my confidence after this?

well on this web cam site,i was in a girls room. one her friends said i wanted everyone to be like me. it was unexpected. i never said that. just now i went back and asked her why,she said bc i called her sister a foo when she was leaving,so i said,cant she take a joke? so the girl said wtf? stfu! then she told me i looked like a 10 year old . Her and her friend said they were 14,i highly doubt it,bc they both look young. She then banned me to ever being in contact with her online at all. I had to do this. I was so mad and sad at the same time. I said trash about her and what she did to her sister on her comments. she hasnt read it yet,but i dont know what will happen. How can i feel better? i feel like hurting myself. :( please help me