Sixty-five years ago, Dr. Norman Vincent Peale revolutionized the publishing world with his enormously popular book “The Power of Positive Thinking.” Fifty-one years later, the equally popular book and video “The Secret” proposed the same argument: that focusing on the things that we want (i.e., being positive or optimistic) can pay big dividends. Some people have interpreted this attitude as meaning that tangible material items (a bigger home, a new car, etc.) will come their way if they just focus on that object long enough and hard enough. But new studies indicate that the major benefit of thinking positively has less to do with our assets than our immune system. Judith T. Moskowitz, a professor of medical social sciences at Northwestern University’s Feinberg School of Medicine, is being hailed as the scientific patron saint of positivity. She has helped train patients who are coping with a variety of physical challenges …