
Arjuna draws his conclusion: 'Tasmāt'—therefore. Having seen what his opponents miss, he states 'nārhā vayaṁ hantum'—we ought not kill. Not 'cannot' or 'will not,' but 'ought not'—a moral obligation rooted in consequence. They're 'dhārtarāṣṭrān sva-bāndhavān'—Dhritarashtra's sons and our kinsmen. Both labels apply. His devastating question: 'kathaṁ hatvā sukhinaḥ syāma'—how, having killed them, can we be happy? Not whether it's justified, but whether it leads to happiness. You can win completely and lose what makes winning worthwhile. The teaching: sometimes what you're entitled to do would make your life unlivable.
How this ancient wisdom applies to your daily life

The verse makes a devastating shift: from 'am I justified?' to 'will I be happy?' You can take that dream job that destroys your marriage, sue your family and win, sabotage your friend for the scholarship—you'd be completely justified. But 'kathaṁ hatvā sukhinaḥ syāma'—having destroyed your own people, how can you be happy? Justification addresses the past: what they did, what you're owed. Happiness addresses the future: who you'll become, what life you'll have. Sometimes what you're entirely entitled to do would make your life unlivable.

What are you justified in doing that would make you miserable? Imagine you've won, destroyed them, gotten everything you're entitled to. Now what? Is that person happy?