The 39-year-old superstar was shown crying after missing an 105th minute penalty in the Selecao's Euro 2024 last-16 victory over Slovenia on Monday.
Despite multiple attempts at goal and then Jan Oblak saving his spot kick, Ronaldo could not pierce Slovenia's sturdy defensive wall and eventually the match finished goalless across 120 minutes, leading to penalties.
Taking Portugal's first spot kick, this time the former Real Madrid hitman did find the net and his team triumphed 3-0 on penalties after Diogo Costa saved all three Slovenia efforts.
Ronaldo is now on a redemption trail and his side face France next in a rematch of the 2016 final which Portugal won in Paris to clinch their first ever European Championship.
Eight years ago Ronaldo was not the hero either, going off early with an injury and seeing the lesser-known Eder striking in extra-time to defeat Les Bleus.
Without a goal to his name at the Euros, the all-time men's leading international goalscorer with 130 strikes has at times appeared desperate.
"I will always do my best for this shirt, whether I fail or not, and I'm going to do this my whole life," Ronaldo told Portuguese television channel RTP.
"I've been doing this for 20 years -- as you saw I missed the penalty, but I wanted to be the first to score.
"We have to take responsibility... you can't be afraid, I've never been afraid to face things head on, sometimes I get it right and sometimes I don't, but giving up is something you'll never hear attached to my name."
Ronaldo made his Euros debut in 2004 in his homeland but Portugal came up fractionally short, losing in the final against unfancied Greece.
The forward, who went on to star for Manchester United, Madrid and Juventus, now plays for Al-Nassr in Saudi Arabia.
If he scores in the Euros he will become the oldest ever goalscorer in the competition's history -- so long as his 41-year-old team-mate Pepe doesn't find the net.
'The last Euros'
Ronaldo is appearing in a record-extending sixth Euros and has scored 14 times in the competition, far ahead of French great Michel Platini's runner-up tally of nine.
"It's undoubtedly the last Euros (for me) of course," said Ronaldo.
"The most important thing about this career I have made is the enthusiasm that I have still to be here."
Portugal coach Roberto Martinez agreed and said Ronaldo's tears were a sign of how much this all means to him.
"When you see a player, the only player to play in six Euros, with the desire and that belief (of a) young man, those emotions are incredible for someone who has won everything and experienced everything," said the Spanish coach.
"He doesn't need to care that much and that is why I thank him... I was certain he had to be the first taker (in the shoot-out) and show us our way to the victory.
"Everyone is very proud of our captain. He gives us all a lesson, to have real high standards and never give up."
Ronaldo had multiple free-kicks either off target or saved by his former nemesis, Atletico Madrid's Jan Oblak.
The striker has scored at every major tournament he has played at but is without a goal in eight Euros and World Cup games, having taken 20 shots without success in Germany this summer.
Ronaldo is aiming to put that right against France.
"We will now have a difficult game against France, who are the favourites to win the competition along with Germany and Spain, but let's go to war," he said.
"We will fight until the end."
