And why?
Because in the brief time of such passion the very highest and finest emotions of which human nature is capable are brought into play.

In that time more than at any other hour in life do men become unselfish, unselfish at least toward one human being.

Not only unselfishness but self-sacrifice is a desire peculiar to the period.

The young man in love is not merely willing to give away everything that he possesses to the person beloved; he wishes to suffer pain, to meet danger, to risk his life for her sake.

Therefore Tennyson, in speaking of that time, beautifully said: Love took up the harp of Life, and smote on all the chords with might, Smote the chord of Self, that, trembling, pass'd in music out of sight.
Unselfishness is, of course, a very noble feeling, independently of the cause.