For an excellent (scientific - insofar as science can be applied to human thought proceesses; Ehrenreich has a PhD in cellular biology), witty, insightful, greatly relevant and important work on the subject of “positive and negative thinking (Ehrenreich recommends realistic thinking, btw) I highly recommend reading her book “Bright-sided: How Positive Thinking is Undermining America.” (She has a brand new book out, “Natural Causes”).