This week I heard an episode of the Writers Almanac (love that little show!) that introduced me to Karl Menninger, 19th-century advocate for the mentally ill, and founder of the Menninger clinic in Topeka. Once, when someone asked him what to do if a person feels he is about to have a nervous breakdown, Menninger replied, "Lock up your house, go across the railroad tracks, find someone in need, and do something for them." He also said, "The central purpose of each life should be to dilute the misery in the world."
Similarly, this is a big theme with President Monson, and also with President Hinckley. Here's a typical example from a talk President Hinckley gave that was reprinted in the July 2006 New Era.