Who was the problem in the relationship

A lot of people have broke up with or left someone In a relationship. If the person who you left in the relationship came back to you or tried to would you consider that you were the problem or the other person was? Sometimes people might out grow each other except I do believe that if you were to leave someone or breakup with them then they come back to you they probably miss you or something about you which lead them to want to be with you again.