सर्वद्वाराणि संयम्य मनो हृदि निरुध्य च। मूर्ध्न्याधायात्मनः प्राणमास्थितो योगधारणाम् ॥

sarva-dvārāṇi sanyamya mano hṛidi nirudhya cha mūrdhnyādhāyātmanaḥ prāṇam āsthito yoga-dhāraṇām

All the gates closed, the mind confined in the heart, the life-breath fixed in his own head, concentrated by yoga,

In plain words: Krishna describes how a yogi prepares at the moment of death. He shuts the doors of the senses, holds his mind still in the heart, gathers his life-breath up into his head, and stays focused through yoga.