Hamilton assumes he had been with McLaren for too long and glad to switch to Mercedes
The 2008 world champion had been groomed by the Woking based team for F1 stardom from his McLaren-sponsored days in karting, but 2012 was his sixth consecutive season on the grid with the same outfit.
Last year, he finished just fourth in the drivers' standings, despite having what many believed was the very best car in the field at season's end.
"I was thankful that I had a car in which I was able to compete with Sebastian (Vettel) and co," he said in an interview with Germany's Sport Bild.
"But maybe I had just been with McLaren for too long.
"Anyway, I realised that I didn't want to spend the rest of my life there. At Mercedes, everything is new, also the challenge -- which is huge.
"And I'm fine with that. I just needed a change of scenery."