"The Notebooks of Malte Laurids Brigge" R. Rilke

For poems aren't, as people think, feelings (one has those early enough) ;
they're experiences. To write a single line of verse one must see many
cities, people, things, one must know animals, one must feel birds
flying and know the movements flowers make as they open up in the
morning. One must be able to think back to roads in unfamiliar
regions, unexpected encounters, and partings which one saw coming long
before; one must be able to think back to those days in one's
childhood that are still unexplained, to one's parents whom one could
not help offending when they brought a delightful gift and one didn't
appreciate it (it was a delight for someone else), to those childhood
illnesses which arose so peculiarly and with so many profound and
difficult changes, to those days in peaceful and secluded rooms, and
to those mornings by the sea, to the sea anywhere, to seas, to nights
of travel that swept along high above, flying with the stars; and it's
still not enough, even when one's allowed to think of everything one
can. One must have memories of many nights of love--no two nights the
same — of the cries of women in labour and of pale, white, sleeping
women who have given birth and are now closing again. But one must
also have been with the dying, one must have sat in a room with the
dead with the window open and random noises coming in. And having
memories is still not enough. If there are a great many, one must be
able to forget them, and one must have the patience to wait until they
return. For the memories are not what's essential. It's only when they
become blood within us, become our nameless looks and signs that are
no longer distinguishable from ourselves—not until then does it
happen that, in a very rare moment, the first word of a verse rises in
their midst and goes forth from among them.