what is the lesson scrooge learns in stave 4 that he had not learned before?

Scrooge believes they are the shadows of what "May" be, but the Ghost says nothing. Scrooge sees his own name on the tombstone, and realizes he was the dead man from before. Scrooge vows to honor Christmas in his heart and live by the lessons of the past, present, and future, such that he may alter his life. The Ghost shrinks and collapses into a bedpost. Scrooge wakes up in Stave 5 a new man. He has learned his lesson. He no longer carries greed and darkness in his heart. He has let in the Christmas spirit: it is a resurrection of his own kind innocent spirit that has remained dormant so many years.