I have just finished reading "smile or die" by Barbara Ehrenreich. Barbara is an author with progressive politics (that is probably the worst bio she will ever get -- sorry). When she was close to 50, she got cancer. Luckily she recovered, but while she was taking chemical therapy, she found the world of positive thinking. There was a lot of pressure to think positive, however she was angry.
After this experience and when she got well again, she investigated the "positive thinking movement." I have read a number of positive thinking books. What I didn't realize was that the positive thinking movement is a very powerful way f brain washing people. For example the advantage of positive thinking for people with cancer is that they complain less to people around them. A similar situation occurs when a person loses their job. Companies are now using life coaches to tell people getting fired the challenge of finding a job is the best thing that could have append to them.
Barbara reviews the literature on whether positive thinking actually helps recovery from illness. It was not clear that it did help.
Now that you know that smiling and being positive is wrong, you are ready to listen to my worries.