Nobility, not perfection.  In The Silmarillion, the Elves' history, like ours, is mainly war, tragedy, and darkness.  They envy us our mortality, as we envy them their immortality.  (Envy is one of the stupidest of sins, the only one that never caused a single moment of even false joy.)  Though Tolkien is both temperamentally and ideologically conservative, the Elves are bad conservatives:  they want to embalm the present.  Seeing the downward slant of the present, they try to preserve the past.  They are not evil like Sauron, who always wants to sing “I Did It My Way”, but they are foolish because they sing “I Believe in Yesterday”.  We too are foolishly Elvish when we want to hold onto our youth, or the initial experience of falling in love, or when we seek the enoughness of eternity that we all innately long for in places where it can never be, somewhere in time.