In Act 1, we encounter Scrooge for the first time. We see that he is a greedy, bitter man. He does not care about the holidays, and in fact, he cares very little about anything that does not help him earn money. He is a lonely man, and does not like to spend time with people. With his bitterness, sadness and cynicism, Scrooge represents the antithesis of the Christmas spirit.
In Act 2, we see that Scrooge has "gone down memory lane." He has been visited by the ghost of Christmas past, and this has reminded him of the man he once was. Scrooge can see, in front of his eyes, his slow transformation into the sad man he is now. This causes him to breakdown and cry for all the things he has left behind and the negative transformation he has been through.