This guy thinks Winnie the Pooh is not a good management guide. He offers Martin Seligman as a better choice.
In that spirit, I'd like to introduce you to the work of Martin Seligman, a professor of psychology at the University of Pennsylvania and long a leading cognitive therapist who has helped patients with depression beat problems previously believed to be insurmountable. The theory of cognitive therapy emerged from the work of Albert Ellis and Aaron Beck in the 1960s and 1970s, and Seligman has been both a popularizer of the field and a researcher and theoretician who has built on Beck's work. Seligman's early work investigated why people feel helpless even when external evidence suggests they're not helpless. For the past 15 years, he has focused on how attitude — optimism in particular — can defeat negative thoughts and help people break free of inaccurate, pessimistic assumptions about themselves and their world.
I read Seligman's book probably 6 or 8 months ago, and it's pretty good. I think that businesspeople tend to be too optimistic already, so I won't recommend it. If you look at the poor decisions made by so many companies, it is because they are emotionally attached to their product, and they think everyone is going to love it and buy it. But that isn't always the case, and you always need a plan B, becaues you may be wrong.