The Serbian ace has won 24 major titles in a glittering tennis career and believes that his record-breaking spell at the top of the world rankings is just as special as winning so many Grand Slams because of the consistency it required.
Speaking to the ATP website, Djokovic said: "There's a lot of debate on what the ultimate challenge in our sport is. From my experience and my career, I would say probably the top two things would be winning the career Slam or Golden Slam, including the gold medal at the Olympics, and staying No.1 for many years.
"The Slams are such as big of every single player and they take a lot of energy to be conquered. So for you to be consistently playing well over and over again, to be a contender for No. 1 in the world, that's probably one of, if not the ultimate challenge.
"Because it requires a 24/7 attention to every single detail when it comes to physical recovery, preparation, mental training, anything really that revolves around an individual athlete, because in the end of the day, you have to do the job yourself on the court. I have been blessed to achieve these many great things."
Djokovic is on a quest to win a 25th Grand Slam crown and explained how his targets have evolved over the course of his career in the sport.
He said: "When I was a kid, I was dreaming of playing and winning Wimbledon... Back in 2011 when I achieved my childhood dream to win Wimbledon and become No. 1, I was of course deeply satisfied, but then I was only at the time 23 and I was, like, 'OK, I still have to play hopefully another 15 years.' I still want to set new objectives, new goals.
"I'm an ambitious guy, so I thought if I won that year in 2011, three out of four Slams and played semis of the French, why wouldn't I go for it (the career Slam)?
"So when it was achieved in 2016, it was huge. It was a relief for me because I have put so much pressure on myself primarily and then of course there is always expectations of the people around.
"When that was done, it was just the primary sensation or emotion that was just a relief. 'OK, I've done it, now I can move on and think about something else.'"
