The two were both at Juventus in the Italian Serie A a few years ago, before Ronaldo moved on to Manchester United and then Saudi Arabia.
Kulusevski himself left Juve, moving to Spurs in the Premier League after an initial loan.
"To not be satisfied with being good, but to be the best every day," said Kulusevski, per Fotboll Skanalen.
"That's the only thing that matters. As hard as it is to try to be the best.
"I think that you learn over time, that you begin to understand much more about how the world and the brain work. You can't be 17 and know everything.
"Yes, I always change. I'm starting to get to know my body. When I was younger, I didn't understand when (Cristiano) Ronaldo told me: 'You will get to know your body'. Because I didn't know my body then.
"But now I'm starting to understand my strengths and weaknesses, how I can improve. So I feel like everything is getting easier.
"I know how to train the day before a match, two days before a match, what to do when I'm tired and so on. All the little details that in the end make a big difference."