Real were thumped 5-2 in Jeddah, despite Barca having goalkeeper Wojcieh Szczesny sent off on 55 minutes.
Flick said afterwards: "We must learn from each game. We can still do things better, we have a young team. We have not played well in some weeks. The situation in the league is not good, but we have already discussed that in the dressing room.
"We won the Supercopa as a united team , but we are Barça and we are obliged to improve. We are not looking back. We are living in the moment and we must admit that it was spectacular.
"The way we play is important. We made mistakes today and that is what we have to correct. When you have the ball, everything is easier."
He added, The game we played at the Santiago Bernabéu gave us confidence in our ability to win this type of game and it has been demonstrated. We are getting better and better."