Experience

Life is the only real counselor; wisdom unfiltered through personal experience does not become a part of the moral tissue.

You must learn day by day, year by year, to broaden your horizon. The more things you love, the more you are interested in, the more you enjoy, the more you are indignant about, the more you have left when anything happens.

I believe that imagination is stronger than knowledge -- myth is more potent than history -- dreams are more powerful than facts -- hope always triumphs over experience -- laughter is the cure for grief -- love is stronger than death.
 
Regret

Make it a rule of life never to regret and never to look back. Regret is an appalling waste of energy; you can't build on it; it's only for wallowing in.