MANY translate Yoga as ‘union’. Please understand, Yoga is not ‘union’. It is ‘uniting’. Yoga is not a noun. Yoga is a verb. Yoga is not an end result. Yoga is a process. As Lord Krishna says in the Bhagavad Gita, Yoga is being what you are without expectations and without attachments. Yoga is not doing but being.
There is nothing to achieve by practicing Yoga! Shocked? Many people have told you that Yoga will cure you of asthma, it will cure you of chronic pain, it will cure you of high blood pressure and so on. Perhaps it does; but not because of what you practice, but because you believe it does. That is why your intention behind your actions is so important in yoga.
Yoga unites the mind-body-spirit system. Actually, what unites them is not just the exercises that you perform, but the intention with which you perform them. When you perform an action with a conscious intention, you create a physical memory which gets embedded in your muscles.
So it is essential to start any Yoga practice with a clear intention of what you want from it - health, strength, enlightenment, anything. Before you perform the asanas (physical postures), with full awareness of your intention, visualize the posture you plan to adopt. Go through in your mind every single step of that asana. Then practice that asana.
Just by sitting comfortably in any position with your spine erect to allow energy flow, you can derive the result of any asana through intention and visualization. However difficult it is to believe, this is the truth!