Commenting on that definition of yoga, F. Yeats Brown, author of Yoga Explained, adds: "Yoga is a discipline whereby the disciple attempts to harmonize the rhythms of the Self with those of the God it can apprehend, a God who grows greater as the human consciousness expands. It is a method of self-realization, in which spirit and matter are seen to merge in the universal."
I agree with this understanding and definition but that's not the way yoga is presented or taught, especially in gyms and fitness centers. There is too much focus solely upon asana (the poses) separated from the concept that yoga is a practice of union - unifying the lower self with the Higher self, the human self with the Divine self.