Ferrari's Sebastian Vettel has admitted he underperformed at times during the 2018 Formula One season and says he needs time to recover from an "exhausting year".
Despite a strong first half to the year, Vettel was out of title contention with two rounds remaining as he failed to match eventual champion Lewis Hamilton.
Vettel's last victory came at the Belgian Grand Prix in August and in the eight races that followed he scored just 106 points to Hamilton's 177. A combination of collisions and mistakes in France, Germany, Italy, Japan and the U.S.A. contributed to his struggles and saw him lose momentum at a crucial part of the season.
Speaking after Sunday's season finale in Abu Dhabi, he admitted that some of his performances were below par.
"Looking back I haven't been at the top of my game," Vettel said. "I can be better than I was at times this year. I think I need some time for myself. It has been a quite difficult and exhausting year for me."
He added: "I don't think I ever had any problems raising my hand if I made a mistake. I don't think I need to change things upside down but certainly I can adjust and get stronger.
"Having said that though, I think we also had a lot of races where we got everything out of the car and the package and I felt that I did everything I could."
Ferrari has been keen to deflect blame away from Vettel and has admitted to making a mistake with the development of its car around the time of the Singapore Grand Prix. A series of updates around the floor of the car at that time appeared to have a negative impact on performance and were eventually removed for the U.S. Grand Prix, which was won by Vettel's teammate Kimi Raikkonen.
Combined with the death of Ferrari chairman Sergio Marchionne following the German Grand Prix in July, Vettel said the season had been tough for the Italian team.
"We lost our path a little bit halfway through the year," Vettels said. "Things didn't come together so obviously we did a step back towards the end of the year which enabled us to be more competitive again but I think we've understood what went wrong.
"We had a lot of lessons, it was a tough year in general. I think the team is strong and the team has potential. The passing of our chairman, Mr Marchionne obviously had an impact and was tough, so I think it's up to us to look into every single detail and make sure we come out as a stronger group, enabling us to build a stronger package for next year and for the future."