"Self" vs "Other"

There is a question i always have in mind. Why is it hard to sacrifice for one's self, while no matter how much we sacrifice for the other, it always seems endless?

The self, and the other. We commit sins, for the sake of the other. We destroy our lives, for the sake of the other. We take risks, for the sake of other. By the end, was it worth it?

TEACHERS spend their lives planning lessons and getting sick of it for STUDENTS.
MOTHERS spend sleepless nights for their CHILDREN.
A WIFE destroys her life in order not to lose her HUSBAND.
A GIRL would give up her values to stay by HIS side.

Its confusing. Is it a part of human nature to just GIVE GIVE GIVE and not to be given back? Or some people are just cursed.

When we commit ourselves to something, we focus on reaching our goal, and we forget one's "self". Whether it was getting sick, spending sleepless night, destroying our lives, and giving up our values, it never seems enough.

Deep inside us, it hurts to step on the "self". To forget who we are and who we belong to. To erase our past and ignore the present, and only gaze at the future that we drew in our minds. A beautiful pinky future, where Beauty gets married to the Beast who turns out to be a handsome prince, and where Cinderella meets her Prince Charming, and where Sleeping Beauty gets the kiss that brings her back to life. Is that all true? Or are we living a fairy tale with a hopeless-ever-after.