Every person, no matter how great, must practise karma yoga in order to evolve and make himself competent for higher stages of meditation. He must work so hard that karma yoga becomes his life. The maximum results can be derived only by making karma yoga a part of his life. Sannyasa does not mean abandonment of action; it means abandoning the self oriented mode of action. This has been explained in the Bhagavad Gita. Sri Krishna has gone so far as to say:
He who performs his bounden duty without depending on the fruits of his actions,
he is a sannyasin and a yogi, not he who is without fire and without action. (6:1)
This means that the person who acts without caring for the fruit of actions is a sannyasin and a yogi. Nobody in this world works without any expectation of the fruit; one who does is indeed a sannyasin. One should always bear in mind that this has been preached in all religions.