Unhappiness, discontent or suffering results from the tension between desire and the lack of the thing desired. Now there are two possible approaches to overcoming this unhappiness. One is to obtain the object desired, to secure possession of it; the other is to eliminate the desire.

If we carefully examine the happiness that comes from satisfying desire, we would find that such happiness is unreliable and insecure. This happiness depends on external things. These objects of desire are inevitably impermanent, and when we are separated from them we become unhappy. Thus even in the midst of happiness we become vulnerable to suffering.

Therefore the Buddha points out that true happiness is to
be achieved by taking the opposite approach, the approach of eliminating our desires. If we eliminate the desire our mind remains satisfied, content and happy no matter what our external situation may be. The Buddha says that this principle can be carried through
all the way to the total uprooting of craving. This is the cessation of craving, the end of suffering (dukkha) here and now.

Bhikkhu Bodhi, Nibbana