श्रेयान्स्वधर्मो विगुणः परधर्मात्स्वनुष्ठितात्। स्वधर्मे निधनं श्रेयः परधर्मो भयावहः ॥

śhreyān swa-dharmo viguṇaḥ para-dharmāt sv-anuṣhṭhitāt swa-dharme nidhanaṁ śhreyaḥ para-dharmo bhayāvahaḥ

Better one's own duty, though destitute of merit, than the duty of another, well discharged. Better death in the discharge of one's own duty; the duty of another is full of danger.

In plain words: Krishna says it is better to do your own duty, even poorly, than to do someone else's duty well. It is better even to die doing your own duty, because following another's path is full of danger.