Man experiences disappointment through lust, greed, and anger; and the frustrated ego, in its turn, seeks further-gratification through
lust, greed, and anger. Consciousness is thus caught up in a vicious circle of endless disappointment.
Disappointment comes into existence when either lust, greed, or anger is thwarted in its expression. It is thus a general reaction of gross, subtle, and mental entanglements. It is a depression caused by the non-fulfillment of lust, greed, and anger, which together are coextensive with selfishness.
Selfishness, which is the common basis of these three ingredient vices, is thus the ultimate cause of disappointment and worries. It defeats itself. It seeks fulfillment through desires but succeeds only in arriving at unending dissatisfaction.
-Discourses, 7th Ed, p 11