The archer hat to hit the bird by looking at its reflection in the water. I see nothing but the bird to be aimed at. That is concentration. Arjuna's is the power of concentration. Concentration, when developed, becomes meditation.
Yoga is an exact science.
Service and charity expand the heart. The aspirant is now fully equipped for the last lap of the journey. It is the toughest part of the pilgrimage to God. It is full of darkness and the aspirant has to pierce this darkness with his purified mind. The purified mind is the most dependable weapon in the armoury of the spiritual aspirant.