Nico Rosberg said his drive to winning his first world championship in the Abu Dhabi Grand Prix was the toughest race of his life.
Rosberg had to contend with Mercedes team-mate Lewis Hamilton driving deliberately slowly to try to ensure other drivers passed the German.
"I couldn't not think about what was at stake," Rosberg said. "I tried and it didn't work. I had to.
"It was difficult to stay optimistic and in those times it was hard."
Hamilton's tactics in backing up his team-mate from the start of the race ensured an intense afternoon for Rosberg.
He was under pressure throughout and at one stage needed to find a way past Red Bull's Max Verstappen after being told it was "critical" to overtake.
"That was not a nice thing to hear," Rosberg said. "Honestly, that was really bad. A horrible feeling.
"The feelings I had in that battle and right after I passed him, I never want to have those again in my life."
Rosberg said he was not expecting Hamilton to drive that way, but admitted: "Maybe that was a bit naive."
And he admitted to doubting his ability to win the title from time to time during the season, for most of which he has led on points after a series of reliability and other problems for Hamilton.
"I believed in it strongly," Rosberg said. "I was always optimistic but there are always moments when it becomes difficult and even out there today there were some seriously tough moments."
But he added: "It was my best season and I have done my best ever races.
"The last couple of races and especially the last one, that is not the real Nico because the pressure just slows you down.