two poems for people who like that sort of thing, where "that sort of thing" is both "poems" & "valediction" :

FAREWELL! thou art too dear for my possessing,
and like enough thou know'st thy estimate:
the charter of thy worth gives thee releasing;
my bonds in thee are all determinate.

for how do I hold thee but by thy granting?
and for that riches where is my deserving?
the cause of this fair gift in me is wanting,
and so my patent back again is swerving.

thyself thou gav'st, thy own worth then not knowing,
or me, to whom thou gav'st it, else mistaking;
so thy great gift, upon misprision growing,
comes home again, on better judgment making.

thus have i had thee as a dream doth flatter—
in sleep, a king; but waking, no such matter.
--william shakespeare, sonnet lxxxvii (1609).

stop all the clocks, cut off the telephone,
prevent the dog from barking with a juicy bone,
silence the pianos and with muffled drum
bring out the coffin, let the mourners come.

let aeroplanes circle moaning overhead
scribbling on the sky the message he is dead,
put crepe bows round the white necks of the public doves,
let the traffic policemen wear black cotton gloves.

he was my north, my south, my east and west,
my working week and my sunday rest,
my noon, my midnight, my talk, my song;
i thought that love would last for ever: i was wrong.

the stars are not wanted now: put out every one;
pack up the moon and dismantle the sun;
pour away the ocean and sweep up the wood.
for nothing now can ever come to any good.
--w.h. auden, "ix" (1936).