Cyprus recorded a shock 4-4 draw in Portugal in September 2010 but since then new coach Paulo Bento has replaced the sacked Carlos Queiroz and revived the team's fortunes.
"We are much improved but we cannot take it easy and make the same mistakes we did in the first game. Our goal has to be to keep top spot," Ronaldo told Portuguese television.
"We cannot look upon Cyprus as a weaker team. They stole two points from us," added the world's most expensive player.
Portugal's preparations suffered a setback on Wednesday when central defender Ricardo Carvalho, who has played at two European championships and two World Cups, quit the team camp, saying he had been "disrespected."
"I feel in full physical and mental form, as I have shown for my club and country, but if I am made to feel unnecessary and am not told so, then the only way is out," Carvalho said in a statement carried by state news agency Lusa.
"Having earned 75 caps and been deeply dedicated in defending the national side's reputation, I have never before felt so disrespected and wounded in my dignity," added the 33-year-old Real Madrid player.
Fellow winger Nani is also on form, having scored in Manchester United's 8-2 rout of Arsenal at the weekend.
Sporting's Rui Patricio is set to take over in goal from Eduardo, who has been mainly on the bench at his new club Benfica.
"Portugal will be a hard job for us. Our aim is to not let them win and to achieve that we have to be focused and avoid making mistakes," said Nioplias.
