Almost all our suffering is caused by our not having the power of detachment. So along with the development of concentration we must develop the power of detachment. We must learn not only to attach the mind to one thing exclusively, but also to detach it at a moment's notice and place it upon something else. These two should be developed together to make it safe. (CW, 6:38)
To restrain the indriyas (organs) from going towards the objects of the sense, to control them and bring them under the guidance of the will, is the very central virtue in religious culture. (CW, 3:66)
All actions, internal and external, occur when the mind joins itself to certain centers, called the organs. Willingly or unwillingly it is drawn to join itself to the center, and that is why people do foolish deeds and feel miserable, which, if the mind were under control, they would not do.
What would be the result of controlling the mind? It then would not join itself to the center of perception, and , naturally, feeling and willing would be under control. (CW, 1:171)
The flame of a lamp sheltered from wind does not flicker. This is the comparison used to describe a Yogi's mind that is well under control and united with the Atman. (6.19)
From whatsoever reason this wavering and fickle mind wanders away, it should be curbed and brought to abide in the Self alone. (6.26)
Setting that mind firmly on the Self under the direction of a steadfast intellect, one should practice tranquility little by little, and abstain from every kind of thought. (6.25)
You must keep the mind fixed on one object, like an unbroken steam of oil. The ordinary man's mind is scattered on different objects, and at the time of meditation, too, the mind is at first apt to wander. But let any desire whatever arise in the mind, you must sit calmly and watch what sort of ideas are coming. By continuing to watch in that way, the mind becomes calm, and there are no more thought-waves in it. (CW, 7:253-54)