Because we are so imbued with this notion that happiness is something to be pursued by the continual transformation of the external, it can sound odd to hear the Buddha talk of uncovering happiness within. He acknowledged the inevitable presence of disequilibrium, which he called dukkha or suffering, but suggested we seek out its internal causes, understand them and solve the problem by means of internal adjustments. According to his analysis, it is not the objective discrepancy between the internal and the external condition that is the source of unhappiness; it is the desire for the external to change (or not to change as the case may be) which is itself an internal state.

Andrew Olwendzki, Unlimiting Mind