When a country sends its army to war, they don't just teach the soldiers how to shoot and then tell them, "Go to the front!" The great minds of the army prepare (hopefully) wise strategies and tactics to outmaneuver and win the opposing army.
The war against the yetzer hara is compared to a fight between countries.
And since the battle against the yetzer hara is a war, we need strategies to win our war with the yetzer hara. About this, Chazal (Brachos...
4.
The Chovas HaLevovos (Shaar Yichud HaMaaseh 5) teaches, "A chasid met warriors returning from battle. It was a tough war [and they rejoiced that they won]. The chasid told them, 'You returned from a small war.... Be prepared for the great war.'"
They asked him, "What is this greater war?"
The chasid replied, "It is the war against the yetzer hara and his army."
