यदा विनियतं चित्तमात्मन्येवावतिष्ठते। निःस्पृहः सर्वकामेभ्यो युक्त इत्युच्यते तदा ॥

yadā viniyataṁ chittam ātmanyevāvatiṣhṭhate niḥspṛihaḥ sarva-kāmebhyo yukta ityuchyate tadā

When his subdued thought is fixed on the Self, free from longing after all desirable things, then it is said, "he is harmonised."

In plain words: Krishna says a person is called balanced when his calm mind rests on the Self and he no longer craves the things people usually want.