Ronaldo is back to his best after scoring twice in victory over Sevilla on Saturday.
He told France Football: "Football is cyclical. When things aren't going well, the fans have to help us. We've won three Champions Leagues in four years, something which isn't easy to do.
"Sometimes things don't turn out so well: the ball hits the post and won't go in, or the opposition goalkeeper puts in a great display. I'd ask the fans to have more faith."