This healthy minded life is a half life, impoverished for its willful ignorance of the other side, the dark and decaying side that always wins out in the end. Those who go through life thinking that the power of positive thinking is all that is needed to get by are like denizens of an imaginary land. For them, the sun always shines, the weather is fine, life is abundance. They don't realize that summer doesn't last forever, that the summer hut they've built for themselves will not stand the first frosty winds of autumn, never mind the winter. Such are the acolytes of perpetual joy. They embrace a philosophy that can only sustain itself in the vigor and energy of youth. When that goes, like the summer, they find themselves philosophically and spiritually ill-equipped to deal with the new conditions.
William James, The Complete Works of William James
William James, The Complete Works of William James