Wickedness Cannot Produce Happiness
Helaman 13:38–39
38 But behold, your days of probation are past; ye have procrastinated the day of your salvation until it is everlastingly too late, and your destruction is made sure; yea, for ye have sought all the days of your lives for that which ye could not obtain; and ye have sought for happiness in doing iniquity, which thing is contrary to the nature of that righteousness which is in our great and Eternal Head.
39 O ye people of the land, that ye would hear my words! And I pray that the anger of the Lord be turned away from you, and that ye would repent and be saved.
The Prophet Joseph Smith said:
“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.”
(History of the Church, 5:134–35.)