Real conceded an early goal to Valdo, before Gonzalo Higuain and a Raul penalty settled the points for the hosts after a difficult week at the Santiago Bernabeu.
Schuster said: "We made it very difficult for ourselves. We conceded a goal from a set play because we were not concentrating. And what was more important, after Wednesday, was the psychological subject, which worried us.
"But we fought back and showed great character. We're a team that is improving. It has not been a game for the fans, but we fought hard to win."
He added: "This week nothing has changed. It was only the setback of not continuing in the Champions League, but the season is not over. The Liga is an important title and we are doing very well in it.
"My position does not have importance because I have total confidence in the club."