Often we're nice to others because they're nice to us .... Whilst sometimes, it cld just be because we feel indebted to them therefore we're nice to them....

Indebted in a way probably because we've once hurt them, and that we acknowledge, hence we'll try ways and means to make it up to them.... to try to do anything that cld possibly make them happy or even happier....and more importantly or solely for our own's personal interest - to ease the guilt within us....

A final note....whatever that's done is justifiable....