It's foolish to be obsessed with past failures.

Buddhism Day by Day

Wisdom for Modern Life by Daisaku Ikeda
Friday, July 19, 2013:

 

It's foolish to be obsessed with past failures. And it's just as foolish to be self-satisfied with one's small achievements. The present and the future are what are important, not the past. Those who neglect this spirit of continual striving will start to veer off in a ruinous direction.