Regret
"Whatever happens at all happens as it should; you will find this true, if you watch narrowly." - Marcus Aurelius, Meditations, IV, 10
"There are no mistakes. The events we bring upon ourselves, no matter how unpleasant, are necessary in order to learn what we need to learn; whatever steps we take, they're necessary to reach the places we've chosen to go." - Bach, Richard in 'The Bridge Across Forever'
"Things that are done, it is needless to speak about ... things that are past, it is needless to blame." - Kung Fu-tse [Confucius] (551-479 B.C.)
"No matter how far you have gone on the wrong road, turn back." - Turkish proverb