Perhaps, as Kahneman’s research would lead us to expect, Buffett spent less of his life in a positive mood than he would have if, at some point in the 1960’s, he had quit working, lived on his assets, and played a lot more bridge. But, in that case, he surely would not have experienced the satisfaction that he can now rightly feel at the thought that his hard work and remarkable investment skills will, through the Gates Foundation, help to cure diseases that cause death and disability to billions of the world’s poorest people.