Yoga means that which takes you on to a higher dimension or higher perception of life. Asana means a posture. That kind of posture which leads you to a higher possibility is called a yogasana. Among the yogasanas, there are eighty-four basic yogasanas through which one can elevate his consciousness. When we say eighty-four asanas, do not think of them as just eighty-four postures. These are eighty-four systems, eighty-four ways of attaining. A yogi masters only one asana. This is known as asana siddhi. Asana siddhi means one is able to sit in a particular way with absolute ease. Right now, whichever way you keep your body, it is not at ease. If you sit, it is not comfortable. If you stand, it is not comfortable. If you lie down, it is not comfortable. So what the hell to do with this? If you give your body to the process of yoga, slowly you will see the body becomes at ease. If you sit like this, it is absolutely at ease. It is not trying to be some other way.
The way hata yoga is happening in the West, it scares me because all kinds of yoga is happening. You need to understand this: yogasanas are not exercises. Yogasanas are subtle processes to direct and activate your energy in a particular direction. Why I am stressing on this is because generally with exercise, the attitude is, "the harder I do it, the better it is." Asanas or yoga should not be practiced hard. This is not in competition with somebody else. You must completely drop that attitude here. It is very important that you do it with full awareness, very gently with as much awareness as you can.