We human beings don’t want suffering. We want nothing but pleasure. But actually, pleasure is nothing but subtle suffering. Pain is blatant suffering. To put it in simple terms, suffering and pleasure are like a snake. Its head is suffering; its tail is pleasure. Its head contains poison. Its mouth contains poison. If you get near its head, it’ll bite you. If you catch hold of its tail it seems safe, but if you hold onto its tail without letting go, it can turn around and bite you just the same. That’s because both the head of the snake and the tail of the snake are on the same snake.
Both happiness and sadness come from the same parents: craving and delusion. That’s why there are times when you’re happy but still restless and ill at ease — even when you’ve gotten things you like, such as material gain, status, and praise. When you get these things you’re happy, but your mind isn’t really at peace because there’s still the sneaking suspicion that you’ll lose them. You’re afraid they’ll disappear. This fear is the cause that keeps you from being at peace. Sometimes you actually do lose these things and then you really suffer. This means that even though these things are pleasant, suffering lies fermenting in the pleasure. We’re simply not aware of it. Just as when we catch hold of a snake: Even though we catch hold of its tail, if we keep holding on without letting go, it can turn around and bite us.
So the head of the snake and the tail of the snake, evil and goodness: These form a circle that keeps turning around. That’s why pleasure and pain, good and bad are not the path.
– Ajahn Chah, Theravada, Thai Forest Tradition.