The Buddha knew that because both happiness and unhappiness are unsatisfactory, they have the same value. When happiness arose he let it go. He had right practice, seeing that both these things have equal values and drawbacks. They come under the Law of Dhamma, that is, they are unstable and unsatisfactory. Once born, they die. When he saw this, right view arose, the right way of practice became clear. No matter what sort of feeling or thinking arose in his mind, he knew it as simply the continuous play of happiness and unhappiness. He didn’t cling to them.
– Ajahn Chah
“The Peace Beyond”