Jeffrey R. Holland

...negative speaking so often flows from negative thinking, including negative thinking about ourselves. We see our own faults, we speak—or at least think—critically of ourselves, and before long that is how we see everyone and everything. No sunshine, no roses, no promise of hope or happiness. Before long we and everybody around us are miserable… We should honor the Savior’s declaration to “be of good cheer.” (Indeed, it seems to me we may be more guilty of breaking that commandment than almost any other!) Speak hopefully. Speak encouragingly, including about yourself

Jeffrey R. Holland, “The Tongue of Angels,” Ensign, May 2007, 16–18

Harold B. Lee

Happiness does not depend on what happens outside of you but on what happens inside of you. It is measured by the spirit with which you meet the problems of life.
Harold B. Lee, "A Sure Trumpet Sound: Quotations from President Lee,” Ensign, Feb. 1974, 78.