According to Osho, suffering arises not from people, events, or the intellect itself, but from our attachment, expectation, and identification with thoughts. When happiness is tied to externals, we oscillate between pleasure and pain. Cultivating upeksha—equanimity and the witness attitude—loosens this tie; without craving or aversion, success and failure pass, and suffering falls away.
We suffer because we cling to things and expect them to make us happy; if we let go and just watch, the pain fades.