Positive thinking is just one small part of positive psychology. Plus, as an approach to well-being, positive thinking only helps you to the extent that it yields one or more positive emotions. The problem with positive thinking is that it sometimes just stays up "in the head" and fails to drip down to become a fully embodied experience.
Barbara FredricksonPositive emotions are not trivial luxuries, but instead might be critical necessities for optimal functioning.
Barbara Fredrickson