Purport

Bhagvan Shri Krishna after reminding Arjuna about his natural duty as Kshatriya and renoucncing the same at crucial moment is sinful, explains the personal and social loss of ignoring duty.

Bhagvan explained Arjuna, that his(Arjuna’s) whole honor and fame is because he is a warrior. To fight for the protection of Dharma, society and humanity is but his prime duty. If he leaves this war, people will immediately conclude that he has run away from war field afraid of his life. People will mock him and will ridicule using unbearable languages. His honor as a warrior will be lost forever.
For a honourable person such loss of honour is worse than death.