Jenson Button says he is left with mixed feelings about leaving the Brawn GP team, but the world champion claims it was something that he had to do.
Button clinched his first world title with the Brackley-based team this year, but decided to move to McLaren for 2010 to partner Lewis Hamilton.
The world champion insisted he needed a fresh challenged after reaching his goal with Brawn, but admits he is sad to be leaving the team he has been with for seven years.
"It's something I've felt I need to do in my career," Button told AUTOSPORT.
"Everything has always been aimed at winning the world championship as it should be and with Honda or Brawn as it is now, we achieved that goal in 2009.
"I'm very excited, but also very sad to leave a team that I've been with for seven years. But all good things come to an end and we ended on a high."
The Briton, who picked up two AUTOSPORT Awards on Sunday evening, said he is finally getting used to the idea that he is the world champion.
"After the race in Brazil it was an emotional moment and I was just knackered basically," he said.
"I'd run out of steam because it was so stressful. Then you go through weeks of just waking up and not realising what you've achieved, other days you wake up and realise I've achieved my goal - I am world champion.
"When you spend so much time away from racing which I've done in the past few weeks, to come to the awards really brings the emotion back and it's a perfect way to celebrate the season.
"I have a couple more awards ceremonies and sports personality on Sunday, so it's a pretty intense and exciting week and it's great to have won these awards that so many great drivers have won before me."