The result means Real could clinch the title on Thursday with a win against Villarreal.
Courtois remarked, "Winning the nine matches after the break says a lot because it's not easy to play at difficult grounds like La Real, Athletic, Espanyol... They are teams that were playing for something and it's not easy.
"Today Granada have given everything and in the first half we played well and scored two goals, in the second half we didn't start well and conceded a goal, but we knew how to dig in and that's important. It's a good win and I hope we can finish the job off at our own stadium."
He added: "A lot of people think that because we're Real Madrid, we win every game, but it's not easy. At difficult grounds anything can happen. In LaLiga there is a lot of quality, a lot of teams play well. The matches are difficult and you don't always win, but we have done. We have two more cup finals left and we have to win them."