Let me paraphrase an incident I read in a book. The author says "I rescued a snake from a dangerous situation. And in return, it bit me. It did what its nature was 😄"

The thing us that people only give back what they have inside them. It is often disappointing to expect the returns in our favour. There are good people and bad too. Nevertheless, our character is ours and we are supposed to elevate it.

About relationships particularly, I would say that, no matter how loving and caring the companion may be, relationships build on reciprocity. Without giving love and care back, it is injustified to keep on expecting the same care always