चेतसा सर्वकर्माणि मयि संन्यस्य मत्परः। बुद्धियोगमुपाश्रित्य मच्चित्तः सततं भव ॥

chetasā sarva-karmāṇi mayi sannyasya mat-paraḥ buddhi-yogam upāśhritya mach-chittaḥ satataṁ bhava

Renouncing mentally all works in Me, intent on Me, resorting to the yoga of discrimination, have thy thought ever on Me.

In plain words: Krishna tells Arjuna to offer all his work to him in his heart and to stay focused on him. Using wise judgment, he should keep his mind on Krishna always.