Veteran Portugal defender Pepe admitted on Thursday he lost sleep before the World Cup because he was worried he would miss the tournament through injury.
The 39-year-old became the third-oldest outfield player to feature at a World Cup on Monday, starting for the first time in almost two months in the 2-0 win over Uruguay.
Pepe suffered a knee sprain in early October and made his return as a substitute for his club Porto in their final match before the World Cup on 12 November.
"When I had the injury, I couldn't sleep to be honest," Pepe told a press conference, a day before his team play South Korea in their final group H match.
"I couldn't sleep because I wanted to recover as soon as possible and play in another World Cup, to contribute to my national team, to achieve victory.
"So the journey seemed very long, but it is now over.
"I have to look ahead, to look forward with objective of doing the best I can to secure a win."
Portugal have already qualified for the last 16 but can guarantee top spot if they win or draw against South Korea on Friday.
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Danilo Pereira started at centre-back alongside Ruben Dias in the first game but fractured three ribs in training, allowing Pepe to step in and produce a strong display to shut out Uruguay.
He said even after 130 appearances he was still enjoying playing for his country.
"I can't say if it's the last World Cup that I will play," said Pepe.
"I am here to enjoy the tournament. It's a privilege to do what I love, to play football."
Portugal have one of the stronger squads at the tournament, featuring Cristiano Ronaldo, Bruno Fernandes and Bernardo Silva.
However, Pepe believes that talent alone will not be enough to earn Portugal their first World Cup trophy.
"We have several ingredients, and if we don't put all the ingredients together, as our coach has said, (it doesn't work).
"If we prepare a salad, you can't have tomato on one side and onion on the other side, you have to put them all together.
"We have a high-quality national team, but unless we work very hard, respect our opponents and do what our coach says, we won't benefit so much from this quality."