Quote 19
NORA: "Yes, a wonderful thing!—But it is so terrible, Christine; it mustn't happen, not for all the world." (2.322)
Nora thinks the wonderful thing will be when Torvald sacrifices himself for her, proving his love. She's also terrified of this because it will destroy him. In the end, Torvald just doesn't love her enough to sacrifice himself.
Quote 20
NORA: "It was necessary he should have no idea what a dangerous condition he was in. It was to me that the doctors came and said that his life was in danger." (1.193)
It's interesting that all Nora's lies to Torvald stem from an act of love.
Quote 21
NORA: "You might give me money, Torvald. Then I will wrap it up in beautiful gilt paper and hang it on the Christmas Tree." (1.38-1.40)
There's a good chance that Nora wants money for Christmas just to pay down her secret debt.