Every person must know that whenever a spark of G-dliness illuminates him, or when he awakens himself with new inspiration to serve Hashem, the forces of evil incite him even more. Thus, he must be very strong so as not to fall because of this. He shouldn’t get discouraged by it, even if it happens thousands and tens of thousands of times, G-d forbid. Instead, he must strengthen himself very much through the Torah—meaning, he should strive to think of chiddushei Torah. And even someone who isn’t capable of this should, at the very least, engage in Torah study with a fresh awakening, and try to fulfill all the words of the Torah with simplicity and sincerity, never leaving the path of the Torah, G-d forbid.
Even though according to the flaming inspiration of a person’s heart, he yearns to be holy, separated from material things, and completely detached from the empty desires of this world, and so on—nevertheless, if his yetzer hara overpowers him and incites him specifically now even more than before, he shouldn’t despair because of this, G-d forbid. Rather, he should strengthen himself not to step outside the simple path of the Torah, at the very least, and fulfill the verse: “Don’t be overly righteous… and don’t be overly wicked” (Koheles 7:16-17)—meaning, don’t become very wicked, G-d forbid, just because you wanted to be very righteous and didn’t succeed, since the Torah shatters and nullifies all the Sitra Achara that wants to provoke us, G-d forbid.
(Likutei Halachos, Netilas Yadayim 4)