Yoga is as much about working on the body as it about working on the mind. A still and focused mind is not agitated by emotions, plagued by doubt or swayed by the actions of others. All of us are blessed with a restless, unsettled Monkey Mind. Psychologists reckon that the average person conducts a non-stop internal conversation with him/herself amounting to a staggering 300 words per minute!
So this is why we do yoga… to channel and harness our stream of thoughts. Even though Yoga is now largely considered a physical practice, the asanas originally existed purely to allow the student to sit in lotus posture on order to meditate.
When we learn to control our mind and have single-mindedness we experience things in all their beauty. Like eating for example, you really taste the food and can get maximum enjoyment out of the experience. Or listening to what somebody is saying to you, with absolute focus you really get the nuances and subtleties of the conversation. With a concentrated mind everything is Technicolor, more vivid and more meaningful.
So when you come to your mat to practise, be in the asana and nowhere else, as soon as your mind wonders from your action you are losing the beauty and joy of what you are doing.