Elizabeth Bishop, 1911 - 1979 (http://en.wikipedia.org/wiki/Elizabeth_Bishop)

  The art of losing isn’t hard to master;
  so many things seem filled with the intent
  to be lost that their loss is no disaster.

  Lose something every day. Accept the fluster
  of lost door keys, the hour badly spent.
  The art of losing isn’t hard to master.

  Then practice losing farther, losing faster:
  places, and names, and where it was you meant 
  to travel. None of these will bring disaster.

  I lost my mother’s watch. And look! my last, or
  next-to-last, of three loved houses went.
  The art of losing isn’t hard to master.

  I lost two cities, lovely ones. And, vaster,
  some realms I owned, two rivers, a continent.
  I miss them, but it wasn’t a disaster.

  —Even losing you (the joking voice, a gesture
  I love) I shan’t have lied.  It’s evident
  the art of losing’s not too hard to master
  though it may look like (Write it!) like disaster.