Yoga gradually draws our lower self, the ego, in alignment or in harmony with our higher Self, and there is union.
Yoga is the process or means by which we achieve yoga, union.
We do poses, mediate, do pranayama or work with the breath, and practice the yamas and the niyamas to draw into greater alignment–to “yoke” the self to the Self.
It is the means by which we keep our lives in this proximal zone of harmony.
The Every Day Yogi 