Four-time Grand Slam champion Naomi Osaka of Japan says she is building self-confidence and belief while trying to be less of a perfectionist on and off the tennis court.

The defending US Open champion beat 87th-ranked Czech Marie Bouzkova 6-4, 6-1, in 93 minutes on Monday to reach a second-round matchup with Serbian qualifier Olga Danilovic.

Osaka said she didn't feel pressure but was nervous nonetheless as she tries to make life changes.

"I tell people I'm a perfectionist. For me, something that's less than perfection, even though it might be something great, is a disappointment," Osaka said. "I don't really think that's a healthy way of thinking, so something that I really want to change.

"In this tournament I just want to be happy knowing I did my best and even though I didn't play perfect I was able to win a match in two sets, or if I have to battle, play a match in three sets -- know that I made a couple mistakes, but it's OK at the end of the day because I'll learn.

"It's not really a tournament thing. It's more like a life thing. I hope I can keep this mindset throughout my life going forward."

Osaka withdrew from the French Open after one match over mental health issues, saying she didn't want to talk with reporters after matches, and skipped Wimbledon as well.

This week, she has opened up about her feelings on social media and to journalists, saying she needs to respect herself more.

"It has been a gradual situation," she said. "There were multiple events in my life that led me into thinking the way that I do.

"For me one of the biggest things is hearing a little kid telling me that I'm their favorite player or I'm a role model. Instinctively the first thought in my mind is 'Why?'

"I feel like I have to sort of embrace more the feeling, the honor that they're telling me that, and I should believe more in myself.

"I feel like if you don't believe in yourself, then other people won't believe in your self. It's more like a realization thing."

Osaka said her nervous energy over the first round of a Grand Slam mingled with the excitement of having spectators back after no fans were allowed in 2020 due to Covid-19.

"It was definitely a bit weird feeling. But I think I was more excited than nervous in the end," she said.