The Rare Fortune
Mokṣa-bhāgya ('the good fortune of liberation') refers to the rare combination of circumstances — birth in a time and place where the Lord's grace is accessible, encounter with a qualified ācārya, receipt of the three rahasyas (the secret teachings), and the ripeness of accumulated karma that enables surrender — that makes liberation attainable in this lifetime.
Why It Is Called 'Fortune'
Sri Vaishnava theology holds that the soul has wandered in saṃsāra for countless births. The vast majority of births do not provide the specific combination needed for liberation: access to the śāstra, an ācārya who transmits the rahasyas, the mental readiness to receive and act on the teaching, and above all the Lord's own grace that draws the soul toward surrender. When all these converge, it is indeed a bhāgya (fortune, good luck) — not merely personal achievement.
Gratitude as the Appropriate Response
Recognizing one's mokṣa-bhāgya generates profound gratitude — toward the Lord who orchestrated the circumstances, toward the ācārya who transmitted the teaching, toward the guru-paramparā that preserved the tradition, and toward the Āzhvārs whose devotion made the path accessible to all. This gratitude is expressed through kaiṅkarya (service) and through the practice of prapatti itself.
Urgency
Acknowledging one's mokṣa-bhāgya also creates appropriate urgency: this fortune may not repeat in future births if it is not used. The teaching of the ācāryas emphasizes that the human birth — especially one endowed with access to the sampradāya — is precious and its opportunity must not be wasted.