The 36-year-old's comments come after he was on the verge of retiring last year following a string of disappointing performances.
However, having triumphed in the first race of the season in Qatar, all thoughts of hanging up his helmet for good have vanished.
"I feel good. I have good motivation," Rossi told Autosport. "I like my job because it's also my passion, like all the guys here.
"For me if you have a good life and do good training you can ride at the top until you are 40 or so. It's not like athletics.
"What makes the difference is more the motivation and the concentration. I think mostly it's the motivation."
Rossi also admitted that he has been re-inspired by the fact that races nowadays are a lot closer and more about strategy than speed.
"I'm very happy because in the last years the races have changed," the seven-time champion said. " There was a time with [Casey] Stoner and [Jorge] Lorenzo when the races were finished after three laps. It was difficult and boring.
"Now it looks like for some reason it's changed with Marc and there's more battling and strategy to the end."