Being rejected by YC is far from a "real punch to the stomach". The point of the article is absolutely right. You need a quasi-inexhaustible supply of rock-hard abs to run a start-up. Sometimes, things go very wrong. As the comments on http://danieltenner.com/posts/0005-starting-up-with-a-friend... showed, it can oh-so-easily happen that you find yourself losing your best friends over your start-up.

After I launched my first start-up, my father's advice was: "Are you prepared for the possibility that it might all fall apart in complete disaster in 6 months?" I didn't know how right he was, but having that in my mind certainly helped prepare me.

I'll close with a quote from the ever-insightful "If" poem by Kipling:

  If you can make one heap of all your winnings 
  And risk it on one turn of pitch-and-toss,
  And lose, and start again at your beginnings
  And never breathe a word about your loss;
  If you can force your heart and nerve and sinew
  To serve your turn long after they are gone,
  And so hold on when there is nothing in you
  Except the Will which says to them: 'Hold on!'

  ...

  Yours is the Earth and everything that's in it,
  And - which is more - you'll be a Man, my son!