Moses told the Jewish people, "If you go out to [an optional] war...."
Devarim 21:10
Our ability to succeed in our Divine mission to vanquish evil in the world at large is directly proportional to our success in vanquishing the evil within ourselves. The theater of our inner spiritual battle with evil is daily prayer, in which we strive to empower our Divine souls over our materialistic, animal drives.
What, then, is the spiritual correlate to the "optional" war? Are we not obligated to confront every instance of evil we perceive within ourselves?
The answer is yes, but there is another way to vanquish our inner negativity besides confronting it directly in prayer: studying the Torah. Studying the Torah fills our consciousness with Divine awareness, and this awareness can largely dissipate the evil within us. Whereas the direct confrontation in prayer requires strenuous effort, the effect of Torah study is virtually effortless.
Thus, whenever there is an option to do away with evil through Torah study, taking the route of direct engagement in prayer becomes an "optional" war. Eliminating evil through Torah study renders the need to battle evil in prayer unnecessary, transforming prayer into the simple, serene expansion of Divine consciousness.
From Kehot's
Daily Wisdom #2