Increased respect for others' wants and needs. You can't (and shouldn't) always get your way. Sometimes we fail because we cross the line in exercising our power, pushing people to do things for the organization that are not in their best interests as human beings. Failure can increase our awareness of appropriate limitations to power and help us learn to respect the boundaries of those we lead. 

Recognition that our idea needs some more work. Do your homework, make some adjustments and try again. (Edison logged in over 9,000 failed experiments before finding the right combination to produce the light bulb.)

Humility and a deepened resolve. Leadership requires both humility and courage. (Churchill became a better human being for having experienced the colossal military failure at Gallipoli. It led him to pen the words "Success is not final, failure is not fatal: it is the courage to continue that counts.")