The five-time major winner will open her 2020 campaign in Brisbane after being awarded a wildcard by organisers in preparation for the Australian Open later in January.
“To be fair when I was younger I never saw myself playing past 30,” the 32-year-old Russian told reporters in Brisbane.
“But I still feel there is a lot in me to give. I still have a lot of fire in me and I am big competitor.”
Sharapova has not played since a first-round loss to career-long rival Serena Williams at the US Open in August.
She has slipped to 133 in the world rankings after a 2019 season ruined by a shoulder injury which limited her to 15 competitive matches.
“As long as the shoulder stays healthy and my body allows me to, I hope there is a lot of time left for me,” she said.
Sharapova won the Brisbane title in 2015 and joins a high-class field for next week’s event spearheaded by Australia’s world number one Ashleigh Barty and Australian Open champion Naomi Osaka.
World number two Karolina Pliskova is also playing as are fellow top 10 stars Elina Svitolina, Petra Kvitova and Kiki Bertens.
“It’s a fresh start after a tough last season,” said Sharapova. “There were a lot of ups and downs, there were times when I was ready but the shoulder wasn’t.
“But I have had a fairly good off season and I am motivated to compete. At this point in my career when I have that feeling, it’s a good sign.”
The Brisbane International begins on January 6, with Sharapova then scheduled to play the Kooyong Classic exhibition event in Melbourne before the opening grand Slam of the year from January 20.
Meanwhile, Japanese star Kei Nishikori pulled out of the Australian Open and the inaugural ATP Cup Monday as he continues to struggle with an elbow injury that has kept him out since the US Open.
The former world number four, who has slipped to 13, said he was disappointed not to be able to begin his season as hoped for in January.
“Unfortunately I have to pull out of the ATP Cup and the Aussie Open,” he said in statement.
“Today, together with my team, we have made this decision as I am still not 100 per cent ready or healthy to compete at the highest level.
“This decision was not taken lightly as Australia is one of my favourite places to compete,” he added.
Nishikori’s elbow needed surgery in October and he has not played since.
Yoshihito Nishioka will replace him as the top-ranked player in Japan’s ATP Cup team in Perth. Yasutaka Uchiyama also withdrew from the event earlier this week, with Toshihide Matsui called up instead.
Nishikori’s absence follows Britain’s Andy Murray also pulling out of both tournaments over the weekend with a pelvic injury.
The innovative ATP Cup, from January 3-12, offers $15 million in prize money and a maximum of 750 singles and 250 doubles ATP rankings points in the new men’s warm-up tournament for the opening Grand Slam of the year.
It will see 24 nations split into six groups, with eight teams emerging from the round-robin stage to compete in the knockout phase.
Sydney will host the finals, along with group games which will also be held in Brisbane and Perth.