Normally we think our happiness is contingent upon external circumstances and situations, rather than upon our own inner attitude toward things, or toward life in general. The Buddha was saying that dissatisfaction is part of life, even if we are seeking happiness and even if we manage to find temporary happiness. The very fact that it is temporary means that sooner or later the happiness is going to pass. So the Buddha said that unless we understand this and see how pervasive dissatisfaction or duhkha is, it is impossible for us to start looking for real happiness.

-- Traleg Kyabgon Rinpoche