World number one Novak Djokovic remains highly motivated by the prospect of raising his game to even greater heights, despite acknowledging that the 2015 season has been the best of his career regardless of whether he wins the ATP World Tour Finals yet again.
Djokovic is one match away from a fourth successive title at London's O2 Arena after a 6-3 6-3 victory over Rafael Nadal on Saturday, which levelled the duo's head-to-head record at 23-23.
Roger Federer, who defeated the Serbian during the round-robin stage, or Stan Wawrinka will provide the opposition on Sunday.
Ahead of his 15th successive final, Djokovic said: "Regardless of the outcome of tomorrow's match, the season will still be the best that I had."
Three of Djokovic's 10 grand slam titles have been secured this year, only a French Open final defeat to Wawrinka denying him a clean sweep.
Nevertheless, Djokovic added: "There is always room for improvement, so that's something that honestly excites me and motivates me to keep on going.
"I've had a terrific career and I'm very proud obviously with my team to be able to achieve what I have achieved in the last 10 years of professional tennis, but I still feel like I want to do more and I can do more.
"Hopefully the health, fitness serves me, the fresh mind, and I can do more things in the future."
Nadal hailed his semi-final conqueror as "almost unbeatable" after going down in straight sets.
Djokovic said: "I don't feel unbeatable, but it does definitely feel great when I'm playing the way I played today, when I feel like I'm dictating the pace, the match itself, most of the rallies, I feel like I'm on top of my opponent.
"I've had so many wins this year that, of course, make a difference in terms of the approach, the optimistic approach to the matches and the confidence level I feel on the court.
"It's quite different when you know you haven't lost too many times. Especially against Rafa, I won the last, what, three times we played against each other. That all plays a major role in the mental approach to these match-ups."