In context of the physics of friendship, can anyone let me know about the real meanings of secrifice?
The idea of sacrifice can be analyzed in three contexts, that of free will, determinism, and paradox. Being the study of mechanics, modern physics is not clear on the issue of free will vs determinism. There exists no less than eight distinct widely respected interpretations of Quantum Mechanics and many believe this issue is ultimately insoluable. That being the case, I shall give you my own paradoxical physical views on the subject.
Virtue is its own reward, to have a friend you must first be a friend.
R. W. Emerson
Using this definition of friendship we can then move on to define sacrifice as merely a social convention, an abstract an relative concept. If a person freely chooses to "sacrifice" their life for another is it really a sacrifice? If they have no choice in the matter and everything is deterministic, again is it really a sacrifice? Paradoxically then sacrifice can be seen as selfish.
Harmony does not seek harmony,
And so is naturally attained;
But habits are intent upon harmony,
And so cannot attain it.