By serving the spiritual master, you keep your weapon always sharpened. And then take help from Krsna, the words of spiritual master sharpen weapon and yasya prasadad bhagavata…, and the spiritual master is happy, then Krsna immediately will help. He gives you strength.
Suppose you have got a sword, sharpened sword, but if you have no strength, what will you do with the sword? Krsna will give you the strength, how to fight and kill the enemies. Everything is described. Therefore Caitanya Mahaprabhu (said) guru-Krsna-krpaya (CC Madhya 19.151), make your weapon sharpened by the instruction of the spiritual master and then Krsna will give you strength, you’ll be able to conquer.”
-Srila Prabhupada, Room Conversation; May 7, 1976, Honolulu