User blog comment:SliverV1/Riddles/@comment-1874176-20110914172829

It can not be seen, it can not be heard,

Its beautiful 'though it often hurts,

It isn't wine but goes to your blood,

It feels so good.

It isn't gold but it makes you rich,

An iron heart goes soft 'cause of it.

It isn't fire, but it burns hot,

Tell me: what is it called?

(Its the chorus of a German song; I translated it and changed it a little to make the rhymes fit [more or less].)