Even if you don't believe it

atha cainaṃ nityajātaṃ nityaṃ vā manyase mṛtamtathāpi tvaṃ mahābāho naivaṃ śocitumarhasi

And even if you think it is always being born and always dying, mighty-armed one, you still should not grieve like this.

What it means

Krishna changes approach. Suppose, he says, you don't accept what I've said about the eternal Self. Suppose you believe everything is born and dies, again and again. Even then, grieving like this doesn't help. It's an argument that works whatever your beliefs.

The story

Krishna is a patient teacher. He doesn't demand that Arjuna accept his view. He meets him where he might be, sceptical, materialist, unsure. Calling him mahabaho, mighty-armed one, he reminds Arjuna of the strength still in him.

In your life

Picture a hospice nurse speaking with a family, some religious, some not. She finds words that comfort everyone. You don't need the same beliefs to support someone. Meet people where they are.