The Chelsea defender, 21, as been one of the success stories of the season, ousting £35million Brazilian David Luiz from the team and making the centre of defence spot his own.
But he admits life in the Premier League is difficult compared to the Bundesliga, where he played on loan last season.
“Personally I’m more tired than normal, because playing in Germany you get two weeks off over Christmas, so I’m used to that,” said Christensen.
“Coming back here maybe the most difficult part is the mental side of it. The body is prepared for it from pre-season – but mentally it is difficult to keep your concentration – well it is for me anyway.”
Christensen gave yet another assured display on Wednesday night as Chelsea kept their fifth clean sheet in six matches but failing to score, as Arsenal held them to a goalless draw in the first leg of their Carabao Cup semi-final.
So impressive though have been Christensen’s performances since returning from a two-year loan spell with Borussia Moenchengladbach in the summer though, that Chelsea awarded the Dane a contract keeping him at the club until 2022.
But on the same day, manager Antonio Conte revealed that he had been keen in that same summer to sign Dutch defender Virgil van Dijk, who eventually joined Liverpool from Southampton two weeks ago in a world record £75m deal.
And Christensen said: “You can’t get comfortable here. Even with the players we have here now in the changing room.
“That is why it is so mentally hard, because every time you play you have to perform and you can’t afford to make major mistakes.
“I’m happy the club see a future for me here. I did. I hope that is what is going to happen. I tried to keep out of it as much as possible and focus on football. It was an easy choice to sign.”
Christensen, who now has 14 caps for Denmark and has been at Chelsea since he was 15 after being snapped up from Brondby, has become that real rarity at Stamford Bridge; a player coming through the ranks to establish himself in the first team.
“I’m happy with the way it has gone for me this season,” he said.
“It’s not an easy team to break into. The two seasons I had away from Chelsea prepared me and I said to myself that if I wasn’t ready now I would never be.”
Chelsea now have to go to the Emirates for the second leg of the semi-final on February 24 as the underdogs in the semi-final, after missing a hatful of chances on Wednesday night, Christensen two of them.
“In the end they didn’t get a goal but to begin with we wanted to win at home and get a good advantage,” he said.
“We are disappointed we didn’t win at home and disappointed we didn’t get a goal. That’s the way we like to play – we like to score goals. But in the end we are happy we didn’t give anything away.”
Since Luiz was dropped after a row with Conte over tactics following the 3-0 Champions League defeat at Roma, Chelsea are ready to let the Brazilian go, either on loan or permanently, if they can find a replacement as cover.