Likutei Moharan 72:1/ליקוטי מוהר"ן ע״ב:א׳

1There are times when a person has a thought of returning to God. At that moment he becomes an upright individual. Following this, he seeks to act on his heart’s arousal to repent and so wants to travel to the tzaddik. But once he is on the way, the evil inclination rises up against him and his original enthusiasm abates. And then later, when he comes to the tzaddik, the evil inclination’s assault against him is even greater, so that he loses his enthusiasm altogether. Do not be troubled by this; do not let your thoughts about this confuse you.

2Know, the reason for this is that when he originally had a thought of returning to God, on account of the good that was awakened in him, the action he took at that moment killed his [evil] inclination. His former evil inclination was eliminated: he killed it through the thought of repentance and the act of that moment. But afterwards, when he wants to travel to the tzaddik, a different evil inclination rises up against him. This is because “anyone who is greater than his fellow man, his [evil] inclination is also greater” (as our Sages, of blessed memory, taught in Sukkah 52a). He now has a stronger evil inclination than previously. Therefore, unless he strengthens his resolve against it, this new evil inclination will gain the upper hand and his original enthusiasm will abate. He needs to fight anew, even harder, against this new evil inclination that he encounters.