The 33-year-old has enjoyed a glittering career for both club and country, winning five La Liga crowns, three UEFA Champions League titles, two European Championships as well as the World Cup in 2010.
After being a mainstay in the Real goal for the best part of 15 years, Casillas was used solely in the cup competitions by Carlo Ancelotti last season, with Diego Lopez taking his place for La Liga fixtures.
Casillas appeared rusty as a result, making a mistake that led to Atletico Madrid's goal in the Champions League final, as well as committing costly errors as Spain's World Cup defence ended in a dismal exit at the group stage.
And ahead of Real's UEFA Super Cup final against Sevilla in Cardiff, Casillas admitted his usually high standards had dropped off towards the end of last season.
"I haven't been at my best in the last few games for Real Madrid and Spain, but I have analysed and learned from them," he said.
"I have been through worse moments in my career. You go through good moments and bad moments. Everything is temporary. I have not been at the level I was when maybe people became spoiled.
"You have to grin and bear it and face up to situations like this. I have always done so and I am not going to hide now.
"I understand that when you play for Real Madrid you are always being watched and your name is talked about when things are good and when they are bad.
"Luckily, in my case it has almost always been when things are good.
"I don't feel targeted. The club has treated me very well, I have no complaints. I want to push myself even harder than last year."
