Sichos ha-Ran 79
Translated by Rabbi Aryeh Kaplan, Rabbi Nachman’s Wisdom (Breslov Research Institute) pp. 191-192
When one begins to attach himself to a great Tzaddik and truly serve G-d, he is often filled with great confusion and evil thoughts. The evil was always there, but only now it is surfacing.
A pot of water may seem perfectly clear. But when it is placed on a fire and begins to boil, all its impurities are brought to the surface. One must stand by and constantly remove these impurities. The original purity is merely an illusion. With a little heat the impurity surfaces. But when these impurities are removed, the water is truly pure and clear.
The same is true of a person. Before he begins serving G-d, good and evil are completely mixed together within him. The impurities are so closely united with the good that they cannot be recognized. But then this person comes close to a true Tzaddik and begins to burn with great feeling toward G-d. He is touched with the heat of purification, and all the evil and impurities come to the surface. Here again one must stand by and constantly remove the dirt and impurities as they appear. In the end the person is truly pure and clear.
Purification requires this period of agitation and confusion. In the beginning a person is totally immersed in the material. He then begins to come close to G-d. It would seem possible to remove this dirt and impurity at once. But his mind is completely intermingled with this mire. Were it to be removed immediately, his mind would be drawn out with it. Therefore, one must be purified little by little, in gradual stages.