Lewis Hamilton says he is still hungry for success in Formula 1 despite achieving his childhood ambition of winning his third title last year.
The Mercedes driver is "energised and excited" before the new season, which he starts as favourite after two consecutive world titles in 2014 and '15.
"Now it is just to see where I can go, into the unknown," the Briton said.
"I don't know how far I can go, how long I will go on in F1."
The 31-year-old added: "I am going into a new chapter in my life and I will see where it takes me."
The first race of the season is in Australia on 20 March.
Hamilton said that he was motivated by "my love for the sport and cars; my love for wanting to be able to take the car to the edge, to the unknown, to an area most people can't".
He added: "Those who said I would not succeed, and not amount to anything, I am going to continue to prove them wrong and smile in their face as I do so."
It is nearly five months since Hamilton clinched the 2015 title at the US Grand Prix last October but he said he still found it hard to come to terms with the fact that he had equalled the title tally of his hero Ayrton Senna.
"I still pinch myself every day to think I used to go home from school and put the video in and watch Ayrton and now I have matched him in a similar amount of races in terms of results," Hamilton said.
"But he still has more poles than me so I still have more targets in that sense."
However, Hamilton, who first won the drivers' championship in 2008, said he was not motivated by trying to match the achievements of specific drivers who have won more titles than him.
"People have said: 'Do you want to match Sebastian Vettel or Michael Schumacher?' he said. "That was never a goal for me.
"I don't know how long I will be as good as I have been. But that's the exciting thing about life; you don't know what's around the corner so I will give it everything I have got."
Rosberg confident of strong challenge
Hamilton's team-mate Nico Rosberg, who has been beaten into second place in the past two years, said: "There's a cool battle with Lewis coming up again.
"It is a challenge I really look forward to, to try to beat him more often than not, somehow.
"Realistically, it is going to be tough because he has been better the last couple of years. He is the favourite but it will be a great battle and that's what I enjoy."
The German, who said his confidence had been boosted by a strong run of form at the end of last season, expects a tougher challenge from Ferrari this season.
"At the moment Ferrari look like the biggest threat and it is a serious threat because they are very, very close," Rosberg said.
"I hope we are still in front. For sure, we will be challenging for wins at least but let's wait and see."
Reins loosened a little
Mercedes F1 boss Toto Wolff says the team had "reduced" the number of rules they impose on their drivers in defining the acceptable limits of their battle.
This is partly because they have no choice following the introduction of severe restrictions on what teams can tell their drivers over the radio, and partly because they feel they can be trusted to fight on track without too much interference.
"We entered the season with a little more confidence without losing the plot," Wolff said.
"The current narrative is about the rivalry between Nico and Lewis. We understand it can get a little controversial because they are fighting for the drivers' title.
"They equally understand the spirit in the team. I have no doubts it is going to be OK this season, with a few hiccups now and then."
New contract for Rosberg?
Rosberg's contract with Mercedes runs out at the end of 2016, while Hamilton is starting a new three-year deal.
"Nico is part of the family and we have not started any discussions elsewhere," Wolff said.
"We owe it to our driver to open up these discussions with him before talking to anyone else and understand where he sees his future. We have kept it as little away from him now so he can concentrate on the championship."
Asked whether he was interested in rising star Max Verstappen of Toro Rosso, Wolff said: "In F1 nothing is out of the question. I rate Max and I like (his father) Jos but they are contracted to Red Bull for quite some time and I like the two boys in Red Bull Racing as well (Daniel Ricciardo and Daniil Kvyat).
"You need to be realistic about potential candidates but Nico is my number one priority at the moment. I am going to find out what he wants and then look elsewhere."