Why is Satan Always Angry?

I’m rereading Orson Scott Card’s Ender’s Shadow and there was a little exchange between the nun character Sister Carlotta and another command that had an interesting bit of theology in it.

“Do you know why Satan is so angry all the time? Because whenever he works a particularly clever bit of mischief, God uses it to serve his purposes.”
“So God uses wicked people as his tools”
“God gives us the freedom to do great evil, if we choose. Then he uses his own freedom to create goodness out of that evil, that is what he chooses.”
“So in the long run God always wins.”