There has been, through the millennia, a universal understanding that the word "happiness" refers to several different levels:

SENSORY: that's the "fleeting feeling" you're talking about, usually depending on external circumstances

INNER: This is the contentment, the sense of well being and the sense that life is meaningful that Lyubomirsky referred to. It is not dependent on outer circumstances - which is really the fundamental meaning of containment. I may react, get angry, feel sadness, but there remains an underlying equanimity. Obviously you can't feel sadness and sensory happiness at the same time - that observation may help to make clear the difference between sensory and inner happiness.

INNERMOST: This is self-existent Delight, the basic nature of things. It can't be described to the mind, it has to be known directly. In a way, it has little if anything to do with emotions but rather, it's the state of being in union with all.