Alma, chapter 12, verses 9-11 make it clear that our knowledge and understanding of God’s word and His mysteries will be commensurate with the “heed and diligence” we give to Him and His word:
And therefore, he that will harden his heart,
the same receiveth the lesser portion of the word;
and he that will not harden his heart,
to him is given the greater portion of the word, until it is given unto him to know the mysteries of God until he know them in full.
And they that will harden their hearts,
to them is given the lesser portion of the word until they know nothing concerning his mysteries; and then they are taken captive by the devil, and led by his will down to destruction. Now this is what is meant by the chains of hell.
In the 84th section of the Doctrine and Covenants,verses 43-44, the Lord gives us “a commandment to beware concerning yourselves, to give diligent heed (there are Alma’s words – heed and diligence) to the words of eternal life. For you shall live by every word that proceedeth forth from the mouth of God.” Alma’s statement above makes it clear that diligent heed to God’s word is what allows us to understand His mysteries, and that that understanding is dependent upon an open and a humble heart.
In 1 Nephi 16:28 we learn that the Liahona “. . . did work according to the faith and diligence and heed which we did give unto them.”
When the Savior visited the Nephites, he prayed with them. The scriptures record that His words were so great they could neither be written or spoken by man. But the hearts of the people “were open and they did understand in their hearts the words which he prayed (3 Nephi 19:33). Knowing the mysteries of God will likely be the same for each of us. We will know more than we can tell.
As the apostle Paul wrote, the natural man receiveth not the things of the Spirit of God: for they are foolisness unto him: neither can he know them, because they are spiritually discerned (1 Cor 2:14).
Elder Neal A. Maxwell wrote:
“Even the gospel glimpses are difficult to convey. Brigham Young said, ‘I cannot talk all my feelings, I cannot tell you what I feel and what I see in the Spirit.’ This inability to articulate concerns not only the grand and sacred things but also the simple joys of faith: ‘I cannot say the smallest part which I feel’ (Alma 26:16). Thus it is not only that our eyes and ears have not yet experienced what lies ahead; even if they had, the tongue could not fully express our feelings in the face of such sublime and reassuring things! President Brigham Young’s words remind us of Jacob’s: ‘If I could take away the veil, and let you see how things really are, you would then know just as well as I know, and I know them just as well as any man on the face of the earth need to.’” (That Ye May Believe, p. 200)
Elder Bednar said this about the mysteries of God:
As we ask in faith, we can receive revelation upon revelation and knowledge upon knowledge and come to know the mysteries and peaceable things – that bring joy and eternal life (see D&C 42:61). The mysteries are those matters that can only be known and understood by the power of the Holy Ghost (see Harold B. Lee, Ye Are the Light of the World , 211). David A. Bednar, “Pray Always,” October General Conference, 2008.