Friendship?

Friendship...Is it already the rule in the universe that once somebody treats us well,we should treat him or her back with true heart?

Or else,will it be just my assumption towards true friendship in this world?Why I just feel that it is hard to handle?And instead,I found that true friend is hard to find within your long life journey...

I just hope there is someone who can really take care of my brittle heart and won't let me getting hurt from friendship anymore~