For a warrior, nothing is higher than a war against evil. The warrior confronted with such a war should be pleased, Arjuna, for it comes as an open gate to heaven. But if you do not participate in this battle against evil, you will incur sin, violating your dharma and your honor.
The point, which can hardly be repeated too often, is that differentiation is not separation. The head and the feet are different, but not separate, and though man is not connected to the universe by exactly the same physical relation as branch to tree or feet to head, he is nonetheless connected - and by physical relations of fascinating complexity.
What makes you weep, my friend? In you is all power. Summon up your all-powerful nature, O mighty one, and this whole universe will lie at your feet. It is the Self alone that predominates, and not matter.