Acharya Prashant explains that Arjuna's first and most crucial decision was to choose Shri Krishna over everything else, including a vast army. He emphasizes that if one wants to make the right decisions in life like Arjuna, they must first drop the egoistic insistence on deciding for themselves and instead surrender to a higher guidance. The speaker clarifies that while Arjuna had Shri Krishna in person, for us, 'Krishna' can manifest in any form, name, or shape in the world. The key is to find that source of truth and stay with it, regardless of profit or loss.