Ashakti is attachment. Man gets attached to the objects of the world and is bound thereby. He takes birth after birth and is caught in the wheel of birth and death. Attachment is death. Non-attachment is eternal life.
Anashakti is non-attachment. Ashakti is destroyed by vairagya (dispassion) and viveka (discrimination between the real and the unreal). Look at these - birth, death, old age, disease, impermanence, pain, sorrow, misery, worries, anxieties, fears, etc. Thus you will develop non-attachment.
If you abandon attachment to the fruits of your actions, if you are ever content, if you consecrate the fruits of your actions and the actions themselves to the Lord, you will attain emancipation. Actions will not bind you because you are not doing anything, although you go through the motions of doing something. This is anashakti yoga.
Do not hope for anything. Control the mind and the senses. Give up greed and desire. Free yourself from the pairs of opposites. Be balanced in success and failure. Destroy envy. Though you perform actions you are not bound. Destroy attachment. Be harmonious.
Fix the mind on the innermost Atman - now you will not be bound. You will attain salvation. Practise this yoga. You will purify your heart and attain the goal of life.
Selfless work is yoga. Work is atma-puja (worship of the self). There is no loss in service. Work is transmuted into jnana (wisdom). See the Bhagavad Gita, Chapter IV, Verse 33. "Sarva karmakhalam partha jnane pari samapyate - All actions, in their entirety, O Partha, culminate in wisdom."
Service of the sick is service of the Lord. There is no yoga greater than relieving human suffering. If you serve a sick man for half an hour, it is tantamount to meditating for three hours, or doing japa of Om 21,600 times. Do not think that in service there is loss.
Karma yoga is only a means to an end. It removes the impurities of the mind. As soon as purification is effected, you will have to take refuge in vedanta, the path of jnana (self-knowledge).