An utterly charming, if disreputably misogynist, poem by Yeats, from memory...
Never give all the heart, for love
will hardly seem worth thinking of
to passionate women, if it seem
certain, and they never dream
that it dies out from kiss to kiss.
For every thing uncertain is
part of a dreamy warm delight.
O never give the heart outright
for they for all fond lips may say
have given their hearts up to the play
and who can play it well enough
if blind and dumb and sick with love.
I say all this and count the cost,
for I gave all my heart and lost.
On checking, memory not quite accurate: 'But a brief dreamy kind delight' 'smooth lips' 'deaf and dumb and blind'' he who says this'. Still, given I learned it thirty odd years ago, not so bad...
I think we should all stick in something we've written as well - here is the one poem from my poetaster period that I bother repeating.
In China, craftsmen carve for many years
globes within globes, etched with designs of beasts-
tigers, and dragons. In the smallest globe,
is emptiness to small for us to see,
for them to carve...
And you my love have made
your heart just such a globe
polished and round and perfect even in its hollowness
and now you show us all your sculptured beasts
and you expect us to applaud your skill.