How did Scrooge change from the beginning to Stave 4?

Ovr the course of the story, Scrooge learns that it is never too late to find happiness or make amends to those you've wronged. In Stave 3:

“I don’t know what to do!” cried Scrooge, laughing and crying in the same breath; and making a perfect Laocoön of himself with his stockings. “I am as light as a feather, I am as happy as an angel, I am as merry as a schoolboy. I am as giddy as a drunken man. A merry Christmas to everybody! A happy New Year to all the world. Hallo here! Whoop! Hallo!”

“I will honour Christmas in my heart, and try to keep it all the year. I will live in the Past, the Present, and the Future. The Spirits of all Three shall strive within me. I will not shut out the lessons that they teach. Oh, tell me I may sponge away the writing on this stone!”