"...So when Brian Williams is asking me about what's a personal thing that you've done , and I say, you know, 'Well, I planted a bunch of trees.' And he says, 'I'm talking about personal.' What I'm thinking in my head is, 'Well, the truth is, Brian, we can't solve global warming because I f---ing changed light bulbs in my house. It's because of something collective'."
Newsweek via
http://www.huffingtonpost.com/2008/11/06/candid-obama-genuinely-se_n_141692.html