It should be noted that the nature of the energy currents of some people does not permit them to use this position and they must be given an alternative. But this is very rare. The main work, that done by the mind, has not yet even begun. The way to remove a thief who has entered a room is to go inside the house and throw him out, not to sit outside and shout at him. If we sit on top of a mountain and our mind constantly wanders down to the village below, little is achieved.
Concentration has two enemies, mental agitation, or busyness, and mental torpor, or numbness.
Generally, agitation arises from desire. An attractive object appears in the mind and the mind leaves the object of meditation to follow it. Torpor arises from subtle apathy developing within the mind. In order to have firm concentration these two obstacles must be eliminated. A man needs a candle in order to see a painting which is on the wall of a dark room.