Karma Yoga demands rigorous inner discipline. Watch your mind. Self-deception is waste of time. Scrutinize your inner motives, examine your attitude.
When you do a job for somebody else, you can regard it as labor and invite fatigue, you can do it as duty, often with a sour face, or you can derive pleasure from it, if you change your inner attitude.
What is the karma yogi’s attitude? First and foremost he knows that the ego is a non-entity, and affirms, “Not I, but the Lord in me is the doer of all actions.” Become unselfish, desireless and egoless, you will never have disappointments in life.
Secondly, the karma yogi affirms that he serves the Lord in all. Such an attitude will free you from attachment. You will remember God constantly. You will never look for reward or reciprocity, and therefore you will never suffer a shock.
Regard every one of your actions as worship of the Omnipresent God. Feel it.