"When the cold air comes on in, it kicks the furnace on, and the furnace overwhelms the cold. As the sorrow comes into the heart of a Christian, it kicks on more of the joy. It gets you closer to him, it helps you dig down deeper into him, and the joy kicks up, you might say, like a furnace, and overwhelms the sorrow. That is a picture of a solid Christian. Not a sorrow-less person who is happy, happy, happy, all the time. That’s not the picture. A picture of a real Christian is a person who has a furnace of joy in there that kicks up as the sorrow comes in and overwhelms the sorrow. But the sorrow is there. It is there."
-Tim Keller (1990)