How valuable you find something is subjective. Your appraisal of how much joy something provides is an estimate. You probably accept the possibility that you might be incorrect in how much joy you expect from something before experiencing it, but how could this be true for something you already know from experience?
The joy we associate with present or past experiences is subject to retroactive revision. You’ve no doubt experienced this, though perhaps not conscientiously—and certainly without a label—when you were surprised to learn details about a present or past experience that significantly reduced the value of that experience. An example of retroactive revision is how a spouse reinterprets their marriage after finding out that they’ve unknowingly been cheated on for years.
As you proceed through life, you will learn more and more about the actual value of people, things, and situations. As a result, how important different aspects of life will shift, and the more you learn, the more your valuation will approach more closely to objective value.