Bhagavad Gita · Dhyana Yoga (Atma-samyama Yoga)Chapter 6, Shloka 5 (6.5)

The many meanings of "ātmā". One word six times — sometimes "oneself", sometimes "mind", sometimes "self". The beauty of the verse lies in this: the one who lifts is me, and the one lifted is me too.

Shankaracharya. Uddharet saṃsāra-sāgare nimagnam ātmanā ātmānaṃ … yogārūḍhatām āpādayet — let one raise oneself, drowning in the ocean of samsara, by oneself, and bring oneself to ascend to yoga. Na hi anyaḥ kaścit bandhuḥ yaḥ saṃsāra-muktaye bhavati — there is no other kinsman who can bring liberation from samsara; bandhur api tāvat mokṣaṃ prati pratikūla eva sneha-ādi-bandhanāyatanatvāt — even relatives, on the path to moksha, are often an obstacle because of the bonds of affection. And the enemy: yaḥ anyaḥ apakārī bāhyaḥ śatruḥ so'pi ātma-prayukta eva — even the outer enemy is set in motion by one's own (karma).

Acharya Ramanuja — ātmā = mind. Ātmanā manasā viṣayānanuṣaktena manasā ātmānam uddharet — let one lift the self with a mind that does not cling to objects; tad-viparītena manasā ātmānaṃ na avasādayet — let one not drag it down with the opposite (clinging) mind; ātmā eva mana eva hi ātmano bandhuḥ tad eva ātmano ripuḥ — the mind alone is the friend, the mind alone the enemy.

The difference: Shankara — oneself (one's discernment) is what lifts one out of samsara, and even bonds of affection are an obstacle; Ramanuja — whether the mind is unattached or attached is what makes it friend or enemy.