Joseph Smith
“Happiness is the object and design of our existence; and will be the end thereof, if we pursue the path that leads to it; and this path is virtue, uprightness, faithfulness, holiness and keeping all the commandments of God.” (Teachings of the Prophet Joseph Smith, p. 255.)
Neal A. Maxwell
"First Questioner: How much real happiness is possible in this vale of tears?
"The Disciple: That depends directly on our righteousness. The saints of the first century A.D. in the Americas were described as follows: ’… surely there could not be a happier people among all the people who had been created by the hand of God.’ (4 Nephi 16.) Even in the period around 70 B.C. (which saw much intergroup warfare), the righteous and faithful were happy. Indeed, Alma wrote, ’But behold there never was a happier time among all the people of Nephi, since the days of Nephi, than in the days of Moroni.’ (Alma 50:23.) Fortunately happiness is not totally dependent on what those around us do, therefore.
"Second Questioner: Even so, I see some sad-faced members of the Church, don’t you?
“The Disciple: Too many, of course, but not among those who have received ‘his image’ in their ’countenances.’ (Alma 5:14.) None among those who’ve gotten outside their confining circle of selfishness. Indeed, the Brethren are happy while they cope with serious and somber problems. Someone said it is too bad we don’t preserve the small talk of great men; so, too, the humor of holy men who serve as special witnesses.” (Deposition of a Disciple, p. 18 – 19)