The Brazilian travelled to Qatar still adapting to life on Tyneside after his January 2022 move from Lyon to Newcastle United.
He now heads into this World Cup as Newcastle captain, one of the club's biggest stars, and a leadership figure for Brazil under Carlo Ancelotti.
Speaking to Globo Esporte, Guimarães admitted he left the 2022 tournament frustrated with his own performances, particularly after Brazil's defeat to Cameroon in the group stage.
"It was a learning experience for me, my first World Cup. Obviously, being called up was the greatest achievement of my life. I took all the anguish and negative feelings I had and turned them into work.
"I improved a lot from one World Cup to another. I evolved in many aspects of my game."
The midfielder explained that he used the disappointment as motivation throughout the following years.
"I was very frustrated. But I worked and transformed that pain into good things and positive feelings to improve my game. I feel ready to go again."
Asked what has changed since Qatar, Guimarães pointed immediately to both his personal life and his achievements at Newcastle.
"Much has changed in four years. It feels like ten years passed in four, to be honest."
The 28-year-old is now married and a father of two.
"We changed Newcastle's level. I became one of the club's biggest idols."
Guimarães has become the heartbeat of Eddie Howe's midfield and one of the squad's senior leaders.
"I think I'm arriving at the peak of a player's career, between 28 and 30."
His performances this season support that, with Guimarães describing the recently completed campaign as the best of his career from an attacking perspective.
"I think this was my very good season. It was my season with the most goals and a lot of goal involvements in the Premier League. I've been shooting better. The data showed it. This is the season I've hit the target most often."
Brazil opened their World Cup campaign with a 1-1 draw against Morocco, and although Guimarães did not score, he set up Vinicius Junior's equaliser.
Guimarães also revealed how quickly Ancelotti made him feel important after taking charge of Brazil.
"Since the first call-up and the first conversation we had, I already felt I would be important to him. He made me one of the leaders of the group. It made me want even more, want to be important."
That trust has helped him feel more comfortable representing his country.
"If you compare my importance from the last World Cup to this one, they are completely different levels."
The midfielder also addressed comments from Casemiro, who suggested he could captain Brazil in future.
"When I first arrived with Brazil in 2020, I said I wanted a career like Casemiro's. So to hear that from him was a huge satisfaction."
Guimarães believes his experience leading Newcastle has prepared him for added responsibility at international level.
"I feel ready. I'm the captain of my club. It's an important characteristic."