D&C 101

Lehi taught his son, Jacob -

"Adam fell that men might be; and men are, that they might have joy..." (Book of Mormon | 2 Nephi 2:25)

But maybe not a fullness of joy while in this life. The Lord said to the Prophet Joseph Smith -

"...fear not even unto death; for in this world your joy is not full, but in me your joy is full." (Doctrine and Covenants | Section 101:36)

In this life while being in the world, we experience joy, but not in the fulness thereof. That is yet to come only through obedience to the laws and ordinances of the gospel.

"Therefore, care not for the body, neither the life of the body; but care for the soul, and for the life of the soul.
38 And seek the face of the Lord always, that in patience ye may possess your souls, and ye shall have eternal life." (Doctrine and Covenants | Section 101:37 - 38)

Eternal life or God's life is a fulness of joy.