From Elder John A. Widtsoe's talk on “Temple Worship” given at a meeting of the Genealogical Society of Utah at the Assembly Hall in Salt Lake on October 12, 1920:
But whether in the temple or elsewhere, how do men receive revelations? How did the Prophet Joseph Smith obtain his first revelation, his first vision? He desired something. In the woods, away from human confusion, he summoned all the strength of his nature; there he fought the demon of evil, and, at length, because of the strength of his desire and the great effort that he made, the Father and the Son descended out of the heavens and spoke eternal truth to him. So revelation always comes; it is not imposed upon a person; it must be drawn to us by faith, seeking and working.
With reference to the temple specifically, he says,
The endowment which was given by revelation can best be understood by revelation; and to those who seek most vigorously, with pure hearts, will the revelation be greatest.
I question whether I have ever had the level of desire and effort that Elder Widtsoe has described. If so, it has surely been too scarce, but I am inspired to try harder and seek more after those things that are so eternally important.