The world number two, who lost the top spot and his Wimbledon title when he was beaten by Roger Federer in the semi-finals last month, has won the last three hard-court Grand Slam events.
The 25-year-old bounced back from missing out on an Olympic medal by winning in Toronto and reaching the final in Cincinnati and said he was confident of another good run in New York.
"I feel physically stronger and better prepared than I did last year," Djokovic said at Flushing Meadows on Saturday.
"Mentally I had some ups and downs throughout the season, but I think that was maybe expected in a way. It's normal to have ups and downs."
"It's really hard to expect that I could go five, six months every year without losing a match (as he did in 2011).
"It's been a long season and a long summer, but my year has been really good. I had an exhausting four‑and‑a‑half weeks and I was very glad that I had very successful Toronto and Cincinnati tournaments.
"Coming into the US Open, it was very important for me to get in some hard court matches. Hard court is my most preferred surface so I really look forward to the start of this major."
In each of the past two years, Djokovic has saved two match points against Federer in the semi-finals before going on to win the title.
"His forehand return on the first match point last year was an outrageous way to dig himself out of a huge hole.
"It brings me the nicest memories, that's for sure," the Serb said. "That point saved me from losing the semi-finals and gave me the opportunity to win the title. I did it.
"It was a great shot and something that I will remember forever."
Jelena Gancic, Djokovic's first coach as a child, has been quoted as saying the 25-year-old was dealing with a few off-court issues but Djokovic said they were exaggerated.
"I'm not going to say anything about that because everybody has problems," he said. "I'm sure that you all agree. My problems are much smaller than an average person's problems. I cannot complain about my life."
- Roger Federer