The quote comes from Harvard psychologist William James. The advice below is from a post by Brian Knight titled The Power of Attitude …
“Your attitude is one of the few things in life over which you have total control. Harvard psychologist Williams James: “The greatest discovery of my generation is that a human being can alter his life by altering his attitudes of mind.” If you want to perform at your best, and if you want to maximize your happiness and fulfillment, then you must take control of the life-shaping power of your attitude. Please understand: developing and sustaining a positive attitude is not merely a quick-fix motivational technique. It is a disciplined skill that must be practiced and learned.”
best advice ever. Our life can be changed by changing our attitude.