Why does Lord Krishna instruct Arjuna not to give up his duty even in overwhelming grief?

Lord Krishna instructs Arjuna not to abandon his duty because the grief overwhelming him arises from a fundamental misunderstanding of the self, as the Supreme Personality of Godhead asks how such impurities have come upon one who should know the value of life, warning that they lead not to higher planets but to infamy (BG 2.2). The Lord then explicitly commands him not to yield to this degrading impotence, stating that such weakness does not become him and urging him to give up petty weakness of heart and arise as a chastiser of the enemy (BG 2.3). This compassionate rebuke is meant to elevate Arjuna from the temporary distress of bodily identification to the realization that the soul is eternal and cannot be slain, thereby restoring his courage to act in accordance with his constitutional position. Furthermore, Krishna reveals the science of selfless action by declaring that Arjuna has a right to perform his prescribed duty but is not entitled to the fruits of action, nor should he be attached to not doing his duty (BG 2.47). This instruction establishes that true renunciation is not the avoidance of responsibility but the performance of one's duty with a consciousness fully surrendered to the Divine, free from the contamination of personal desire and lamentation. By fighting without attachment to the results, Arjuna would purify his heart, fulfill his duty as a warrior, and ultimately attain the spiritual perfection that transcends both grief and false peace.