Arjuna was thinking not to fight, but when he heard very minutely, listened Krsna’s instruction, he changed his decision: “No, Krsna wants it. Krsna wants this fight, so I shall do this.” This is krsnanusilanam, cultivating Krsna consciousness — not his decision. His decision was not to fight. A Vaisnava does not want to kill anybody. That is natural tendency. Suhrdah sarva-dehinam [SB 3.25.21]: “A Vaisnava is friend of everyone.” So Arjuna was Vaisnava, a devotee of Krsna. Naturally, he was not inclined to kill and gain the fight. So he declined, that “I will not fight.” But after hearing Bhagavad-gita he decided that “Krsna wants to fight. He wants me…” Nimitta-matram bhava savyasacin. “He says so far that ‘These people who have assembled here, they are already killed. That is My plan. You simply take the credit of becoming victorious over them.'”
So this is krsnanusilanam. Even though I have got one decision in my life, but if I understand that Krsna wants me to do something contrary, I shall be ready to perform this.
From Srila Prabhupada’s lecture on Srimad-Bhagavatam 3.26.46 — January 21, 1975, Bombay