The veteran goalkeeper will play his final game for the club against Arsenal on Sunday.
He told the Daily Mail: "Rollercoaster is the word. It's almost a bi-polar football club, isn't it?
"You are either reaching for the stars like the Champions League or you are going to be relegated. There is not enough middle ground.
"It is almost not acceptable to be doing alright. It's either everything is rosy or the world is caving in. There needs to be more of that sort of 'we're doing alright'."