Balance makes the soul ready for freedom.

This verse presents the fruit of the practice taught in verse 14: one who has cultivated genuine equanimity — 'sama-duḥkha-sukham,' equal in distress and pleasure — becomes qualified for immortality, for liberation (amṛtatva). This is a remarkable teaching: spiritual liberation is not primarily a theological destiny but a functional state available to those who achieve a specific quality of inner relationship to experience.

The word 'kalpate' — 'is qualified,' 'becomes fit' — suggests that liberation is not given but earned through inner development. The person who is not 'vyathayanti' — disturbed, afflicted — by the oscillations of pleasure and pain has, in a sense, already begun to touch the eternal.

They are no longer at the mercy of circumstance. This equanimity is not indifference; it is a stable center from which one can engage fully without being destroyed.

In the language of modern psychology, this maps onto what researchers call 'psychological flexibility' — the ability to experience difficult thoughts and feelings without being dominated by them. High psychological flexibility is associated with greater well-being, better relationships, and more effective action. The Gita is pointing to the same capacity but rooting it in metaphysics: equanimity is not merely a coping strategy but an alignment with the soul's actual nature, which is beyond the fluctuations of pleasure and pain. Practice equanimity not to avoid life but to engage it more completely.