Reappraisal seems to be a successful emotional response to stress. But it can also be an avoidance mechanism. In this article, the author, Dr. Riggio, suggests "positive thinking," a fluffier and more obnoxious name for reappraisal of negative emotions, as a response to stress. The danger of positive thinking is the tendency to forget or minimize the honest negative consequences of whatever you're "thinking positively" enough to live with. We think negatively because we have problems we need to fix- can't positive thinking be an easy way to avoid these problems?
Article mentioned earlier: http://www.psychologytoday.com/blog/cutting-edge-leadership/201210/don-t-let-life-s-hassles-become-stressors