Witsel moved to the Chinese Super League side from Zenit St Petersburg in January 2017 after being linked with a host of clubs around Europe and was instrumental in the club's third-place finish in their first season in the league.
And while Tianjin have also been playing in this year's Asian Champions League, the 29-year-old knows there is a huge gulf in quality compared to English and German football.
"You just need to stay fit if you still have the ambition to play for your country, and this is my ambition so I keep training hard," he told Reuters.
"I make some exercises after training, physically, to stay fit.
"After that, when I go back I adapt myself to the level of our national team because it's 10 times more than here, even in training.
"I did this before when I was in Russia. The championship in Russia is better than in China, but it's not England or Germany so I adapt myself for this.
"And now I'm doing the same."
With a top quality squad featuring the likes of Eden Hazard, Romelu Lukaku and Kevin De Bruyne, Belgium will go to Russia among the favourites and have been drawn to face England, Panama and Tunisia in the group phase.
"When you start a tournament like the World Cup, you start to win the World Cup," he said.
"We have the squad and the team to go as far as we can and we're going to do our best. First is to try to do better than the last World Cup and the last Euro in France.
"It's a good group, but we have our objective is to be first in this one."
Belgium reached the quarter-finals of the 2014 World Cup before being knocked out at the same stage of Euro 2016 under previous coach Marc Wilmots, who has since been replaced by former Wigan Athletic and Everton manager Martinez.
The Spaniard, who was appointed in August 2016, is working to instil a more ruthless approach into the squad, said Witsel.
"He wants for us to have a winner's mentality," he said. "We missed that even in the friendly games.
"Before, sometimes we took them like friendly games. Now, even in training, we make some games with some teams and he wants us to put us all the time in competition and I think that is important because if you want to win a World Cup you have to have a winner's mentality."
(Reporting by Michael Church, Editing by Peter Rutherford)
