But it is not more dangerous than fatalism, the flip side of that coin.
Best to stay somewhere in the middle, be aware of reality, try your best to improve the situation and don't berate yourself too much if it doesn't work, pick up the pieces, learn and try again.
I am reminded of the popularity of sanatoriums back when there was no treatment for TB. There was no evidence that they actually cured people, but they made TB sufferers less visible and easier to take care of.
Similarly people who have been convinced to act happy may have problems that are just as big, but they are more pleasant to be around.
There are real benefits to positive thinking. However cancer survival doesn't seem to be among them. (Citation: http://www.cbsnews.com/stories/2007/10/22/health/webmd/main3...) And certainly when someone loses their job in a bad economy, it is downright dangerous to push a message that can be misread as, "It's your fault for being unhappy about it."
There is a balance to be reached. And our society is far too far off on the "la la, be happy" end. (Disclaimer: I am a person who is naturally inclined to be happy most of the time.)
"Optimists may accomplish more than realists, realists certainly accomplish more than pessimists, but optimists do many times as much damage. For example, nearly all "revolutionaries" and criminals are optimists. Lenin, Hitler, Sadam Hussein, Bernie Madoff, and probably all con-men and burglars were extremely optimistic. The conviction that they will never be caught is nearly universal among criminals. Many, perhaps most, excessive risk takers are optimists." From my blog, back in March, http://williambswift.blogspot.com/2009/03/optimism-is-not-ne... , it is something that has annoyed me for years.
Before someone starts throwing around "Godwin's Law", you should actually go and read a bit about Hitler's life, a serious optimism is one thing that comes across very strongly, from early on, through WWI and his time as a pretty revolutionary, to his decisions in WWII.
Positive thinking is like believing in a Loving God. Neither will provide you material richness, but they might provide some motivation. However everything taken ideologically, be that politics, religion, science, is dangerous.
Best to stay somewhere in the middle, be aware of reality, try your best to improve the situation and don't berate yourself too much if it doesn't work, pick up the pieces, learn and try again.