Before, my classmate and his girlfriend broke up, a part of reasons was mine, and this made me disconsolate for a long time. 

It's all because of jealousy. I get along well with my classmate, we are in a different city, but we often in touch on the telephone (just a greet call for old classmate) Perhaps that is why his girlfriend take me as her love rival. To be jealous is a nature of things for a girl, I know. Maybe someday I'm in love, I’ll be more jealous than her. so I don’t want to say she is wrong, I am right.I’m sorry if I had harmed their love,but I can say we have a clear conscience. 

Later, my classmate told me that the main reason is on himself. He could not bear his girlfriend’s jealousy. She easily said to him broke up when she got angry, He was very tired, after he returned to school,so he’s determined to leave her. Of course we still are good friend now. The truth is that we just good friends. Could it be there was no a real friendship in the relation between the boy and the girl?