Krishna does not dismiss Arjuna's concern. He does not say 'it is easy' or 'you are exaggerating.' He says: Asanshayam — without doubt, you are right. The mind is restless and hard to control. Full agreement. That honesty matters.
But then comes the turning word: 'tu' — but. Yes, it is difficult. But it is not impossible. Two tools can master it. Abhyasa: practice. Doing it again and again. Falling off and getting back on. Vairagya: detachment. Gradually loosening the grip of the things that pull the mind away.
These two — practice and detachment — work like two oars of a boat. Practice without detachment becomes mechanical. Detachment without practice becomes passive. Together, they move the mind steadily toward stillness. Krishna addresses Arjuna with two names here — 'Mahabaho' and 'Kaunteya' — both terms of respect and warmth, as if to say: your struggle is real, and you are strong enough for it.