It is said that the faculty of concentrated attention is at the source of all successful activity. Indeed the capacity and value of a man can be measured by his capacity of concentrated attention.
In order to obtain this concentration, it is generally recommended to reduce one’s activities, to make a choice and confine oneself to this choice alone, so as not to disperse one’s energy and attention. For the normal man, this method is good, sometimes even indispensable. But one can imagine something better.
Ref : Words of The Mother Vol II