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 and share it. 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? Because that is his real nature. He feels happy while working; 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 Vahini, Chap 10, "The Yogis".

All the pains and pleasures man experiences are the results of his own actions
and not due to any act of the Divine. – Baba