Arjuna interrupts. And his interruption is deeply honest. Krishna has painted a magnificent picture — equanimity, sama-darshana, the touch of Brahman. Arjuna has listened to all of it. And now he says: Madhusudana, this sounds wonderful. But I cannot see how it can last. The mind is too restless. Where is the firm ground?
This is not doubt born of disbelief. It is doubt born of experience. Arjuna has tried. He knows what happens when you sit down to still the mind. It runs. It spins. It dredges up old memories and future worries. He is speaking for every person who has ever attempted meditation and felt defeated by their own thoughts.
By addressing Krishna as 'Madhusudana' — slayer of the demon Madhu — Arjuna may be hinting: You can slay demons. Can You slay this one too?