“All that I have written seems to me like straw compared with what has now been revealed to me.” -- Thomas Aquinas
Considered the greatest Christian theologian. After experiencing mystical union, he abandoned writing Summa Theologiae.

The opposite also very equally applies in human life when an individual is graced with mystic union at a young age. Where one is graced with mystic union in the twilight of their life and such a direct experience surpasses all their previous years of indirect knowledge and understanding about it, this is a complete mirror image for the individual who is graced with mystic union at a young age in human life. For once had a taste of The Ultimate, the young mystic's life is ever-fully free afterwards in total Love with That (God), and is completely devoted to passing on that direct knowledge/wisdom of the sacred unity of all Life in God, to inspire and encourage others to come into That for themself (no matter how much they are badgered and abused). For the rest of his life, the young mystic has the good fortune of being without preconception and uncertainty about That, as in the former case. The young mystic is guided the rest of his life by that initiation fully grounded in his being as a constant...

As the great Christian Mystic he was, I cannot speak for Thomas Aquinas, but the latter example here is how mystic union in my life unfolded for me.