Some people object that Karma Yoga (the spiritual discipline of action) involves too much physical strain. They say “I sought only to do good to them, but they ignored my desire and tried to injure me.” Such disappointment makes one lose interest in activity. One wants to do good hoping to derive joy therefrom and distribute joy. When such joy does not arise, despair sets in. But the lesson that Karma Yoga teaches is—do the Karma, as Karma, for the sake of the Karma. Why does the Karma Yogi fill his hands with work? That is his real nature. He feels that he is happy, while doing work. That is all. He does not bargain for results. He is not urged by any calculation. He gives, but never receives. He knows no grief, no disappointment; for he has not hoped for any benefit.
– Sathya Sai Baba