What do we all want, deep deep down? Love? Meaning? Purpose?
The answer is already implied in the question: if we WANT anything, it's the fulfillment of want, of desire. The word for this is joy.
It's different from happiness.
You've probably experienced it, even if you don't remember.
None of the central theological concepts in Christianity make sense without an understanding of joy.
It's not selfish to want to be joyful, in fact, it's selfish to want anything less.
The source of true joy is beyond this world, but joy can be experienced here and now.