All of the buddha's teaching center on one point: to find permanent joy, we must extinguish selfish desire. Selfish desire or craving is the cause of all human suffering, and its importance is underscored by the fact that the Buddha used at least 15 terms for it. Chief among them is 'trishna', thirst, the force which drives all created beings to seek personal satisfaction of their urges, even at the expense of others. Its gratification is so deadly because it almost always brings a surge of satisfaction, reinforcing the compulsion to act on that desire again. If one yields, the next wave of desire will have greater power to compel attention. The most obvious desire is the desire attaching itself to objects in the exterior world - any craving for an experience that one thinks will add to personal pleasure.
The Buddha traced every conflict, even war, back to these basic selfish drives, occasionally couched in self-righteous language. Without understanding the role it plays in human motivation and behavior, we carry it forward into our future lifetimes - not being sated just by satisfying the desires of the present lifetime. The Tibetan Book of the Dead states that these desires remain in consciousness at death (see First Method of Closing of the Womb Door). Because of their power,they condition the choice of a new context for another life, where satisfaction of the same desires will again be pursued. Like a monkey swinging from tree to tree in the forest, the Buddha says, desires keep us leaping from life to life pursuing ever elusive satisfaction:
The compulsive urges of the thoughtless grow like a creeper. They jump
from one life to another, looking for fruit in the forest. (dhammapada 24.334)
Consequently, he described nirvana as the release from trishna itself, from the torment and conditioning of selfish desire. Nir (not) Vana (craving),or, more broadly, extinction of the fires of craving and lust (as well as hate and delusion). According to tradition, these are the words he spoke upon attaining enlightenment:
I have gone through many rounds of birth and death, looking for the builder of this body...But now I have seen you, housebuilder; you shall not build this house again. It's beams are broken; it's dome shattered; self-will is extinguished; nirvana is attained.