I believe that the passage points out how perception is more powerful than reality. When we are distant from the facts, we are motivated by appearance. When we see the facts for what they are, we begen to regret knowing the truth. When we distance ourselves again from the facts, we forget the pain in favor of the more pleasurable thought.
I believe this poem is all about perspective. The man sees a ball of gold. However, once he reaches for it, it is no longer as significant to him. He takes it for granted and thinks it is merely clay. Once he takes a step back (or maybe metaphorically grows older and looks back) he realizes that it really was GOLD, or a golden moment in time that he cannot take back.