This is not like a lesson in physics or quantum theory. It is, however, a lesson designed to show that the catalyst for our joy is a fundamental constant. How much joy we have depends on how much joy we want!
Most people think in the context that joy is like the weather. Our joy is either hot or cold, present or absent, on or off. We incorrectly assume that fixed external factors determine the scale of joy we experience. We believe we have no personal, individual control over our joy.