In the war between Gods and demons, Indra was defeated by demons. Then Indra consulted his Guru Brahaspati . In the meantime Indra’s wife Shachi said, “Dear husband! Tomorrow I shall tie a holy thread around your wrist.”
The Veda- mantras were chanted by the Brahmans, chanting of kar (Omkar) was done and Shachi, with her resolve tied the thread around the right wrist of Indra. It enhanced the power of mind, decision–making, Bhava  and merits. That power of resolve made Indra successful in defeating the demons and bringing victory for the Gods.