Asana is the third limb of yoga. Asana are virtually as ancient as civilization itself. In fact, there are carvings dated from 3000 BCE which show figures sitting in the lotus pose.
‘Seat’ is the most literal translation of asana, ‘aas’ meaning ‘to sit’ or ‘to be’. Its original meaning referred to the seat on which the yogi sat and the manner in which he sat in the practice of meditation.
In Chapter II.46 of the Yoga Sutras, Patanjali defines steadiness and ease, sthira and sukha, as the two key characteristics which make a ‘pose’ an ‘asana’. ‘Pose’ or ‘posture’ do not really convey the true meaning of asana, however, as they do not relay the element of thought or consciousness that must inform each movement of the asana. Bringing consciousness to our asana practice means to be conscious of the entire body; from the surface of the skin on the soles of our feet to those spaces within that respond to the breath. Asana involves a thoughtful process at the end of which a balance is achieved between movement and resistance. Any posture performed without the breath, the mind and the intelligences becomes an exercise, not an asana.
Asana, to a beginner, may seem to deal with the physical body alone, but they have the unique ability to soothe the nerves; the medium between the physiological body and the psychological body, and influence the chemical balance of the brain, which improves the mental state of being, making the mind fresh and tranquil, and relaxing the entire body. Asana exercises every muscle, nerve and gland in the body, keeps the body free of disease, reduces fatigue and soothes the nerves, but their real importance lies in the way they train and discipline the mind. The performance of asana is guided by the role of the breath (pranayama), involvement of the senses (pratyhara) and total concentration (dharana). Asanas are an exploration of self, an engagement of our full potential. They are reflection in action, and, when practiced with discrimination and awareness, bring the body, mind, intelligence, nerves, consciousness, and the self, together into a single harmonious whole.
Physical achievements in asana practice put us in touch with our inner power and accomplishments give us a tangible foothold for our sense of progress, but our goals also limit us because they can represent what we think we are lacking. Thinking that someone who is very flexible can perform asana better than a stiff person is wrong thought. It is not important whether you can touch you head to your knees or whether you can sit in Padmasana. That is not to say that flexibility does not make achieving asana easier, but it is only one element of many necessary for good asana.
Yoga is not progress on the mat. Yoga is conscious action, not ‘learning routines’. Yoga is a practice of growth and expansion. It is in our nature to judge, and we may judge ourselves according to the repertoire of asanas we accomplish and the impressive amount of time we can hold them. What we aim to achieve in the practice of asana is letting go of the fruits of practice, any sense of ‘I’ and ‘you’, any sense of success or failure. Only then can we say that we are practicing yoga.

nothing wrong with a nice aas