When you are talking to someone about your problem or worries and they manage to make everything about themselves? You are telling your friend about your problem instead they start about their own and sometimes they do not even let you talk and get your problem across to them.
I hate it.
i know someone like that, i initially thought she was just trying to relate to my situations and empathize by talking about her own experiences but...later realized she was just doing it for sake of comparisons.