In the Yoga Sutras of Patanjali, yoga is defined as Yogas Chitta Vritti Nirodha. Chitta means the mind, but when you say vritti it means the mind with both its positive and negative thoughts. If you can balance the mind and remove all the distractions, tensions, contradictions, the mind becomes quiet, absolutely quiet. And a calm mind is very essential to go into the higher levels of yoga. This is not just a mental process. It's also how you live on this earth. You cannot live a violent life and sit to meditate for half an hour and say that my mind is free of distractions, not possible. So, Yoga is a way of life.