Yoga karmasu kaushalam.  Yoga does not mean only doing asanas. Yoga also means – jnana yoga or the yoga of knowledge. When you are in devotion, it is called bhakti yoga and when you are doing service, it is karma yoga. Doing service without expectation of any rewards is karma yoga.

Yoga karmasu kaushalam.  You should write this on the wall of your house. Also write something else – Samattvam yoga uchyate. There should be equanimity in the mind. But it is of no use if you only write it on the wall and it only remains there. Instead write this in your head and inside you.

 -Excerpt from a Talk by Gurudev