对人家好等于对自己残忍?

Parents and teacher taught us to be kind to others since young. No doubt, it's a virtue and it makes you happy that others benefit from your kindness towards them.

At times, however, I wonder how true is the saying "Being kind to others results in being cruel to oneself" [对人家好等于对自己残忍]. There were a few occasions that I was exactly in this position. Perhaps, I was being too nice foolish to think that I should help as I felt sorry or responsible towards others when the truth is my help is a nice to have and not an obligation at all. So, in a way, I am at fault for putting myself in a less favourable position.

Anyway, I will continue to help people but I need to be careful not to end up having myself upset instead. Otherwise, I will be the biggest fool! :p Haha.