Joseph Smith
“The great misery of departed spirits in the world of spirits, where they go after death, is to know that they come short of the glory that others enjoy and that they might have enjoyed themselves, and they are their own accusers.” (Teachings of the Prophet Joseph Smith, p. 311)
Orson Pratt
"We might now inquire, what is the cause of this intense suffering and misery? Is it the action of the elements upon the spirit? Is it the materials of nature, operating from without upon it, that causes this distress, this weeping, wailing. mourning, and lamentation? It may be in some measure; it may help to produce the misery and the wretchedness; but there is something connected with the spirit itself that no doubt produces this weeping, wailing, and mourning. What is this something? It is memory, and remorse of conscience; a memory of what they have once done, a memory of their disobedience. Do you not suppose the spirits can have power to remember in that world as well as in this? Yes, they certainly can. Have you never read in the Book of Mormon, where it informs us, that every act of our lives will be fresh upon the memory, and we shall have a clear consciousness of all our doings in this life?
“…In this life, things that may have been erased from your memory for years will be presented before you with all the vividness as if they had just taken place. This will be like a worm upon the conscience; it will prey upon the spirit, and produce unhappiness, wretchedness, and misery. This will cause you to lament, and mourn, and weep after you are cast out from the presence of God.” (Journal of Discourses, 2:239-40)