I’ve mentioned Reb Nachman of Breslov (1772-1810) before, here and elsewhere. I recommend Arthur Green’s biography of Nachman to anyone interested in issues of religion and modernity.

Nachman went through a crisis of faith in the last year of his life, as he lived among advocates of the Haskalah (the Jewish Enlightment, and opponents of Hasidism), dying of tuberculosis. In mid-August 1810, a few months before he died, he emerged from the depths. On Shabbat Nahamu he taught his disciples, as was his custom. From Green’s study:

[His disciple Nathan related that Nahman taught:] ‘Why do you come to me? I don’t know anything at all now. When I teach Torah, there is some reason to travel in order to be with me. But why have you come now? I don’t know anything now; I’m just a simple person.’ He kept on in this manner, repeating two or three times that he was just a simple person who knew nothing at all. He then said that he lived now only by virtue of his one time journey to Erez Israel.  From this he went on to explain the whole awesome matter of how he sustained himself, in time of ‘simplicity,’ by his journey to Erez Israel . . .

The zaddiq therefore must go down and fall into this state of simplicity, and become a truly simple man for some time. In this way he brings life to all the simple ones, whoever they may be . . . All of the simple ones get their life through him, each in accord with how near he is to holiness, and to the zaddiq . . .

The main thing is this:  It is forbidden to despair! Even a simple man who cannot study at all, or one who finds himself in a place where he is unable to study, or the like, should in his very simplicity be strong in worship and in the fear of God. Even at that very moment he is receiving life-giving sustenance from the Torah, through the great simple one, the great zaddiq, who has himself undergone that simplicity and therefore can sustain them all.

Even he who stands on the very bottom rung, God forbid, or in the very depths of hell, may God protect us, should nevertheless not despair. He should fulfill the Scripture:  ‘Out of the belly of the deep I cried’ (Jonah 2:3), and be as strong as he can.  Even he will be able to return and receive the Torah’s sustenance, by means of the zaddiq. The main thing is to strengthen yourself in whatever way you can, no matter how far you have fallen. If you hold on even just the slightest bit, there is yet hope that you will return to God . . . .

After the teaching he became very joyous, and told the people to begin singing ‘Azamer bi-Shevahin immediately . . . Afterwards he spoke with us, very happily, and with an awesome and wondrous grace. He sat through the meal with great joy, talking with us and strengthening us greatly . . . Then he shouted from the very depths of his heart:
‘Gevalt! Do not despair!’  He went on in these words:  ‘There is no such thing as despair at all!’

He drew forth these words slowly and deliberately, saying: ‘There is no despair.’ He said the words with such strength and wondrous depth that he taught everyone, for all generations, that he should never despair, no matter what it is that he has to endure.

– Arthur Green, Tormented Master:  The Life and Spiritual Quest of Rabbi Nachman of Bratslav (Woodstock, Vermont:  Jewish Lights Publishing, 1992), 264-265.