Chris Evans has aged "a thousand years" in his first 10 months as Top Gear presenter, he said.
The revamped BBC Two motoring show will launch on May 29, with Chris at the helm alongside Friends actor Matt LeBlanc and an extensive new presenting line-up.
Writing in BBC Top Gear Magazine, Chris said: "I have never experienced anything in my career that comes close to what it's like to make a single film for Top Gear, let alone a whole hour show ... let alone a whole series."
Ahead of his debut as presenter, he wrote: "There's nothing left for us to be nervous about, we've each aged a thousand years in the past 10 months. We're done.
"There's nothing we can do now except sit back and enjoy our favourite show."
Radio DJ Chris said filming Top Gear was like making a James Bond movie.
He wrote: "There is nothing like it anywhere else in the world of TV. Every scene could be from a movie, every moment teetering on the brink somewhere between disaster and triumph.
"The vast majority of television I have been involved with in the past has been much more 'of the moment', more disposable if you like, as well as being usually live or 'as live'. All of which is so NOT Top Gear.
"TG is more akin to a Bond movie. By the time each episode is broadcast, 95 per cent of its content will have been edited to within an inch of its life to be tighter, brighter and jump off the screen and down your throat."
Chris has previously presented TFI Friday and The One Show.
He stepped into Jeremy Clarkson's shoes in June last year after Jeremy was fired by the BBC following a "fracas" with a producer.
Co-presenting with Chris and Matt will be racing driver Sabine Schmitz, YouTube star Chris Harris, F1 pundit Eddie Jordan and motoring journalist Rory Reid - as well as The Stig.
The June issue of BBC Top Gear Magazine is out on Wednesday May 18.