A younger Maria Sharapova was convinced she would be retired from tennis and have children by now, but it hasn't quite turned out that way.

Instead, she has five Grand Slam titles and millions in the bank, and is listed by Forbes as the top-earning sportswoman in the world.

All in all, the 28-year-old Russian said she had no regrets about how her life has gone.

"I never thought that I'd be playing at this age, honestly," she said in Melbourne, after moving into the Australian Open fourth round.

"When I was born, my mother was very young. I thought I would, I mean, not have kids at 20, but I would have children at this point.

"When you're younger, that's what I envisioned because that's what my family had. You always look to family traditions."

Her personal life remains out of bounds, although she most recently had a relationship with fellow player Grigor Dimitrov.

Sharapova said she had managed to find a good balance between tennis, her personal life and her flourishing business career as she gets older.

As well as being one of the world's most recognisable athletes, she has become a major force in the business world with a series of successful ventures.

They include Sugapova, a candy line, and a Nike apparel collection. Forbes calculated she earned US$29.7 million in the year to last June, naming her as the highest-paid female athlete for the 11th year in a row.

Despite the luxurious life her money can bring her, she said she still likes nothing more than hitting balls on a tennis court.

"I mean, I really love what I do. Although I'd love to sit on the beach and read a book and drink margaritas, after a few days I get bored," she said.

"I know, especially when I miss a couple of weeks... I get back on the court, it's funny, those first few moments where you feel a bit rusty, but the feeling of hitting the ball, even though you're not playing points, when that comes back to me, I'm like, This is what I love to do.

"There's no better feeling."

A reflective Sharapova credited her parents Yuri and Yelena for much of what she has achieved, calling them her "rock" in a life that has seen countless people come and go.

"I've had many different people in my life. Ultimately my parents are kind of the two, you know, rocks that have really guided me in so many incredible directions," she said.

"My father paved this career for me that I just keep following. He just really opened the door to my dream. I'm just kind of living it.

"My mother opened up the world to me culturally, educationally. So I got very different things from both of them."