Andy Murray set his sights on adding to his three Grand Slam titles after securing the year-end number one ranking with victory at the ATP World Tour Finals.
The Briton, 29, beat Novak Djokovic 6-3 6-4 in London to ensure he will stay ahead of the Serb heading into 2017.
"Now that I've got there, I obviously would be motivated to try and stay in that position," said Murray.
"But the majors get me working hard - they really, really motivate me."
Murray, 29, won his third major title at Wimbledon in July, and ended the year on a 24-match winning streak that culminated with victory over Djokovic at the O2 Arena.