World number one Novak Djokovic proclaimed himself fighting fit on Saturday and insisted there was no reason why he cannot repeat his sensational season in 2012. Djokovic won three of the four Grand Slams and five Masters in 2011, became world number one, assembled a 70-6 winning record and banked a season record cash haul of 12.6 million dollars. "This year's success gives me a reason to believe that I can win again. Why not?," said the Serb, who will be based in Abu Dhabi until the end of the year where he will also play in an exhibition tournament alongside Rafael Nadal and Roger Federer. "I think it doesn't make any sense to be anything other than optimistic. I need to believe in my qualities and my abilities and I need to believe that I can repeat the success. "Of course it is going to be an incredibly difficult task to achieve, but you never know, nothing is really impossible." Djokovic's landmark season eventually took its toll with a combination of back and shoulder trouble comdemning him to four defeats in the year's closing stages. But he said he is now injury-free. "Injuries are past at this moment," the Australian Open, Wimbledon and US Open champion told the Gulf News. "I am happy to announce that it has been a couple of weeks since my last match and I have had enough time to recover physically and mentally and to get back into shape. "That's why I have decided to come here and start off the 2012 series strongly by playing against the world's top players."