Krishna says wisdom and realization together can help a person be freed from illness (bondage, evil, or all impurities).
He says that yoga is the king of sciences, king of secrets and the supreme purifier.
Krishna reminds us of the method how attain Self-Realization: Fill your mind with God (energy) in devoted worship (regulating and transforming it into positive eternal).
Steadfastly unite your heart with God alone who is the supreme goal, and you shall realize God.