Selfishness and Relationships

A few weeks ago a friend of mine asked me the following question related to relationships and girls:

Q: Azahar, don't you think you should be selfish in life sometimes?

I replied that no, being selfish is never good. Ideally you should never be selfish.

A relation is not about being selfish. It is about being totally self-less.
A relation is only successful when you put the other person's interests before yours and the other person puts your interests before theirs.

This is difficult to achieve in most relations in this selfish age. Especially in that most sacred a relation enjoyed by a man and a woman united in matrimony under the eyes of God.

A: What is mine will never be taken, what is taken was never mine.

Additional thoughts:
I think it would be even better if we kept mutual interests before personal interests in a relation.