Nachman's central practice is astonishingly simple and is the thing his followers still do. Set aside an hour a day, go somewhere alone, preferably outdoors and preferably at night, and talk to God out loud, in your own language, about whatever is actually going on. Not liturgy, not Hebrew, not formulae. He called it hitbodedut, self-seclusion, and he taught that if nothing comes and the hour passes in silence or in complaining that nothing comes, the hour still counts.
The practice follows from his account of the spiritual life, which is unusually frank about failure. He taught that the experience of God's absence is not a lapse to be got past but the condition of the work. His treatment of the vacated space, the void that had to be cleared for a world to exist, concludes that certain questions arising from it have no answers available in this life, and that the correct response is not a better argument but a cry. Doubt, on that view, is terrain rather than error.
Out of it comes the saying his followers put on walls, that there is no such thing as despair at all. It is not optimism. It is an instruction issued to a man who described his own depressions in detail, and it sits beside his equally emphatic teaching that joy is a discipline to be manufactured deliberately, by dancing if necessary, when it does not arrive on its own.