By serving the spiritual master, you keep your weapon always sharpened. And then take help from Kṛṣṇa, the words of spiritual master sharpen weapon and yasya prasādad bhagavata..., and the spiritual master is happy, then Kṛṣṇa immediately will help. He gives you strength. Suppose you got a sword, sharpened sword. But if you have no strength, what will you do with the sword? Kṛṣṇa will give you the strength, how to fight and kill the enemies. Everything is described. Therefore Caitanya Mahāprabhu (said) guru-kṛṣṇa-kṛpāya [Cc. Madhya 19.151], make your weapon sharpened by the instruction of the spiritual master and then Kṛṣṇa will give you strength, you'll be able to conquer.
Śrīla Prabhupāda, Room Conversation -- May 7, 1976, Honolulu