Who said "Sometimes the hardest thing is knowing when to let go."?

This quote is attributed to Iron Man.

Sometimes the hardest thing is knowing when to let go. - Iron Man

"Sometimes the hardest thing is knowing when to let go."

Iron Man Wisdom

"I am Iron Man."

"Genius, billionaire, playboy, philanthropist."

"I'm not the one who should be worried."

"This is the most important thing I've ever done."

"I'm not angry, I'm just disappointed."

"The best things in life are free."

"You can't have everything in life, but you can have what matters most."

"A woman's intuition is rarely wrong."