Likutei Moharan 250:6/ליקוטי מוהר"ן ר״נ:ו׳

16. This is the aspect of tears <shed> at a time of suffering. On account of one’s experiencing affliction and suffering, he therefore needs the aspect of Providence in order that he might be saved, as explained above. This is why we shed tears, in order to draw through them the elements of Providence and vision. This is because Providence and vision are drawn into the tears, in the aspect of “‘The clouds return after the rain’—this is the vision, which is diminished after crying.” That is, they lessen the sight and take away a portion of the vision. Thus it is that vision is drawn into the tears, as explained above.