I once got a letter from a local fundamentalist Christian who wrote me that my illness was a punishment from god for some sin. This is not so different from the New Age's belief that illness is a lesson. There are those who say that if I have cancer I must have needed it in order to resolve some previous life issues rotting beneath the surface. While regimens of self-management offer patients a sense of choice, autonomy and control at a time when they often feel taken over by disease or an alienating medical establishment, such an approach leaves those who do not triumph with a profound sense of failure. Positive thinking, visualization etc. are techniques that reduce stress and anxiety and helped me deal with tx side-effects, but they probably don't offer the edge we need to defeat cancer.
Fear reduces one to wishful thinking.
To tell people with cancer they need to think positive thoughts is to make them feel guilty if what they feel is fear or anger. The last thing a cancer patient needs is to feel bad about feeling bad. My good friend Barbara sends me posts from the breast cancer listserv from time to time. She wrote that death is integral to the way life is and some people are able to integrate this understanding and experience of reality into their life and self-image without sinking into depression. She wrote about a profound maturity of insight in this way of acceptance.