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President George W. Bush, asked to name a mistake he'd made since 9/11:

You know, I just — I'm sure something will pop into my head here in the midst of this press conference, with all the pressure of trying to come up with an answer, but it hadn't yet...I hope I — I don't want to sound like I've made no mistakes. I'm confident I have. I just haven't — you just put me under the spot here...

Soon-to-retire Microsoft founder and chairman Bill Gates:

I would not change a thing. Sure, we've made mistakes along the way but every one of those has been a chance to learn and do things better.

Presidential press conference, 13 April 2004 [WhiteHouse.gov]
Q&A: Microsoft chairman Bill Gates and CEO Steve Ballmer [Silicon.com]