The Portugal attacker, who netted twice, believes that los Blancos must learn some vital lessons from their error-strewn display against the Turkish champions
Los Blancos had arrived in the Turkish capital with a three-goal advantage from the first leg, but even though their Portuguese talisman gave them an early lead, they were left hanging on at the end after conceding second-half goals to Emmanuel Eboue, Wesley Sneijder and Didier Drogba.
Ronaldo eventually sealed Madrid's place in the final four with an injury-time strike, but the forward was the first to admit that the visitors had performed poorly.
"We're happy to get through after this difficult game," he told Uefa.com.
"This match will serve as an example for us in the future. In football you can't just give chances away.
"They made things hard but, in reality, we were the ones who made things tricky for ourselves.
"We must make sure that we are switched on for the full 90 minutes in future."
Ronaldo's double improved his record in this season's Champions League to 11 goals in 10 games, and he added that he feels that he is currently playing at the peak of his powers.
"I feel good," he said. "I did my job tonight. I am motivated just as my team-mates are. Let's see who we get in the draw."
Madrid will be joined in the last four by group rivals Borussia Dortmund, who recorded a dramatic 3-2 aggregate success over Malaga.