The Team Sky rider dethroned team mate Chris Froome last year to become the third Briton since 2012 to win the Tour.
“It’s strange when you reach the pinnacle, something I’ve dreamt of doing, it takes all the pressure off now,” Thomas said in an interview with the BBC.
“Now I’m just going to enjoy racing, riding my bike and the challenges that brings. But I’ve reached it now. I’ve done it.”
Despite saying he feels like he has “unfinished business” on the Giro d’Italia, where he crashed out in 2017 while in second place overall, Thomas confirmed he will definitely miss the Italian race to concentrate on the Tour de France.
“Maybe I’ll race it next year but this year has always been about the Tour,” he said.
“I did not want to jeopardize the chances of the Tour for anything this year. As defending champion I feel as if I have to go back and want to be in the best shape possible.”
Thomas got his season underway this week at the five-stage Volta a la Comunitat Valenciana in southern Spain — his first race since last September’s Tour of Britain.
The 32-year-old said he will not be expecting much from the Spanish race as he gets up to speed.
“I’m in good enough shape to race, but I wouldn’t say I’ll be going for a podium or a win, it’s just a case of getting going again,” he said. “My initial goals are in April.
“I want to go to the Tour and get there in the best shape possible.”
Thomas opened his account at the Volta a la Comunitat Valenciana with a 13th-place finish in the 10.3km time trial, finishing 20sec behind winner Edvald Boasson Hagen (Dimension-Data).
“I could have ridden it a bit better and saved myself for that climb a little bit more. But that was a good hit out and same again for the next few days,” he said after the stage.