Sometimes a negative emotion arises in you and takes over. Something upsetting occupies your mind and you cannot let it go. Your feelings are like television channels; if you do not like the channel that is on, you can switch to another one. The Buddha called this the practice of "changing pegs," replacing a negative emotion with a positive one. A peg is a big wooden nail that is used to fasten two pieces of wood together. If the old peg is rotten, you drive it out by hammering in a new one.
— Thich Nhat Hanh, Creating True Peace