The Talmud tells a vivid sea-story: Rabbi Yochanan and his companions saw a massive fish raise its head from the water, its eyes shining like two moons, spouting water from its nostrils like two rivers (Bava Batra 73b). Rabbi Nachman of Breslov reads this as a parable about the tzaddik (a righteous person) and the rhythms of holy wisdom.
The tzaddik, Rabbi Nachman explains, is called a "fish" in Kabbalistic symbolism. He normally dwells in the "waters" of upper wisdom. But he cannot remain submerged forever. There are times when he must surface, setting aside his contemplation to deal with mundane matters. As the Talmud teaches, "There are times when setting aside Torah preserves it" (Menachot 99b).
When the tzaddik is immersed in wisdom, his eyes shine like the sun. When he surfaces, his eyes shine like the moon, which only glows when the sun has set. This is not a diminishment. It is a rhythm. "Our eyes shine like the sun and the moon" (Shabbat Nishmat prayer). Sometimes the radiance is direct. Sometimes it is reflected. Both are necessary.
The water spouting from the fish's two nostrils alludes to the two Messiahs, Mashiach ben David and Mashiach ben Yosef, who correspond to "the breath of our nostrils, the anointed of God" (Lamentations 4:20). Through these two Messiahs, even the nations of the world will be drawn to seek God: "All the nations shall flow unto him" (Isaiah 2:2).
Faith is the force that makes this possible. When a person has faith, even illness can be healed, because faith connects to prayer, and prayer connects to miracles that transcend natural law. The tzaddik's rhythmic surfacing and diving models this for everyone: immersion in wisdom followed by engagement with the world, and both illuminated by faith in the God who sustains all things.