33. Vitarka badhane pratipaksa bhavanam.
When disturbed by negative thoughts, opposite [positive] ones should be thought of.
Here, Patnjali gives us a very nice clue on how to control the mind and obstruct those thoughts we don't want. The best way, he says, is to invite opposite thoughts. If the though of hatred is in the mind, we can try to bring in the thought of love. If we can't do that, we can at least go to the people we love and, in their presence, forget the hatred. So, although hatred comes to the surface, we can keep it from coming out or staying long by changing the environment. . . .
We can create a positive atmosphere by looking at a holy picture, by reading an inspiring book, by meeting with a special person or simply by leaving the disturbing environment. This is a very practical point. It is difficult to control negative thoughts while staying in a negative environment unless we have extraordinary strength. The easiest way is to change the environment.
-Sri Swami Satchidananda, The Yoga Sutras of Patanjali