For the sake of a single poem, you must see many cities, many people and Things, you must understand animals, must feel how birds fly, and know the gesture which small flowers make when they open in the morning. You must be able to think back to streets in unknown neighborhoods, to unexpected encounters, and to partings you had long seen coming; to days of childhood whose mystery is still unexplained, to parents whom you had to hurt when they brought in a joy and you didn’t pick it up (it was a joy meant for somebody else); to childhood illnesses that began so strangely with so many profound and difficult transformations, to days in quiet restrained rooms and to mornings by the sea, to the sea itself, to seas, but it is still not enough to be able to think of all that. You must have memories of many nights of love, each one different from all the others, memories of women screaming in labor, and of light, pale, sleeping girls who have just given birth and are closing again. But you must also have been beside the dying, must have sat beside the dead in the room with the open windows and the scattered noises. And it is not yet enough to have memories. You must be able to forget them when they are many, and you must have the immense patience to wait until they return. For the memories themselves are not important. Only when they have changed into our very blood, into glance and gesture, and are nameless, no longer to be distinguished from ourselves only then can it happen that in some very rare hour the first word of a poem arises in their midst and goes forth from them.
Rainer Maria Rilke