For the sannyasin, every thought and action becomes self-evolutive. This is because he has learned to express his karma in the world, in a way which leads him towards liberation and out of bondage. This is karma yoga - the path of evolution through selfless action. Unlike the normal person who creates bondage by his actions (karma), the sannyasin learns to work not for the fruits of his actions, but for enlightenment through the service of all.
Although he has renounced personal life, the sannyasin has not completely renounced karma. That is a very difficult thing to do. Even if one does nothing in the world, yet he is still making karma. Karma is the energy outlet of man. As long as a man is alive, he must act. The nature of his mind will compel him to do so. Even at night during deep sleep, one goes on working on the deeper planes. Karma is not physical mobility and activity, but it is mental and emotional activity. It is the consciousness which is acting to create karma, not the physical body. The fuels of karma are the desires, passions, and ambitions. If a man's desires, passions and ambitions are not strong enough to compel him to act, then at best he will become slow, lethargic and dull. Because man's conscious action is merely an expression of unconscious motivation, the primary site of work is in the unconscious mind. If you want to influence karma, it is not sufficient to stop your actions on the outside. One has to delve very deeply to burn the seeds of karma. This is why it is hypocrisy even for a sannyasin to say 'I will not work in order to minimise karma'. Karma cannot be got rid of until you have attained the highest state of nirvikalpa samadhi - not before.
Therefore sannyasins practice karma yoga in order to purify their minds and to help others at the same time. This is necessary for all sannyasins right up to the final samadhi, from which one does not return. Karma yoga is the sannyasins basic practice for self-evolution. This is why sannyasins work so hard, they are evolving through their labours. In an ashram, every person, no matter how great, must practice karma yoga in order to evolve and to make himself competent for higher stages of meditation.
Everyone suffers from personal problems of some kind. It is unavoidable, due to our conditioning and sensitivity to the environment we live in. How can these difficulties be overcome? Plenty of karma yoga. If one sits around worrying about his personal problems they will only be magnified, until ultimately severe depression sets in. Immersion in selfless service, however, frees one from the ceaseless fluctuations of the mind, and leads to higher awareness.
When the mind is kept busy with an impersonal problem, the personal problems are temporarily forgotten and the mind becomes concentrated on the duty being performed. In this way, the mind grows stronger, by using willpower to motivate actions to the guru or the supreme. Eventually, when awareness has increased and we have the ability to witness the mind like a movie without becoming totally involved emotionally, we have the strength to look back on our problems and face them in a detached manner. It is only in the weak and dissipated mind that problems cause endless suffering.
Karma yoga, total creative involvement in work, puts an end to all our personal problems because it consumes the energy that powers our desires. Pleasure leaves the seed desire to repeat the pleasurable experience, and when we take pleasure in our work, the seed desire is for more work. Mindful, creative activity provides an outlet for all our tensions and talents, and our desires lose their impetus for the energy that impels them is all used up. In this way we become quiet to the depths of our being. Then without even sitting meditation dawns spontaneously.