When our Lord was transfigured on the mount, Peter said "Lord, it is good for us to be here: if Thou wilt, let us make three tabernacles, one for you, one for Moses and one for Elijah." There are, incidentally, no high mountains in Israel. Tabor was high in a spiritual sense: here was revealed a profound mystery that transcends time and space and all this-worldly conceptions. This was why Peter spoke not knowing what he said: his mind could not grasp what was happening and no words could express this experience "not of this world."
So he sought to somehow contain this experience so that it could be comprehended in earthly terms: they would build material structures to memorialize and make concrete the occasion. But then, while he was yet speaking, a cloud overshadowed them and there was a Voice from heaven, God the Father confirming that Christ was indeed His beloved Son. At this, the disciples were cast to the earth, overcome with awe by the incomprehensible event. Indeed, the human heart can not conceive of the good things God has in store for those who love Him and who persevere on the path to salvation.
Until our hearts have been purified and our spiritual eyes opened to divine revelation, we cannot see God face to face, but only, as St. Paul says, as though "through a glass darkly." Without first hand experience of God and the spiritual world, we remain earth bound and our understanding is confined and limited to earthly categories. But as our Lord tells the Apostle Thomas, "Blessed is he who has not seen, and yet believes."
Though we may be mere beginners on the spiritual path, we have the witness of the Scripture and the saints to strengthen and sustain us. By faith (which is the assurance of things not seen) we can become partakers of the divine nature even in this life, ever striving to be made worthy of the transforming power of God's grace.