When we truly practice yoga we change.
The asana are a route into the psychology of the practice. We practice this psychology through our bodies because we experience life through our bodies and what we embody we are more likely to understand. So we practice ahimsha (non-harming) on our mats, reflect on how else we can practice non harming of our bodies and then our minds and the bodies and minds of others.
We practice asteya (non-stealing) on the mat, not stealing from or compromising one part of the body or quality of the breath to express an asana. We might then think about parts of our life out of balance, where might we be stealing from? What might we be stealing in our relationships?
We start to see through the illusion of separation and understand that we only ever see part of a story and that not everything is about us and that we almost always have a choice.
All of this helps us to grow and change. 
This is why we come to the mat even (especially) when life is hardest, because we know that the mat is a place of reflection, strength, flexibility and growth.
