"I need to be two feet into tennis or two feet out," she said in an interview with Vogue.
Former female World Number 1 tennis star Serena Williams has indicated she will retire from tennis this year.
The 40-year-old American player says she will "evolve" away from the sport "toward other things that are important to me" after the US Open in September.
Williams won 23 Grand Slam singles titles and ranks second only behind fellow American Margaret Court, who retired in 1977. She has won more titles in the professional era than any other woman or man.
Williams also holds the joint record of being ranked No. 1 by the Women's Tennis Association (WTA) for 186 consecutive weeks.
She won the French Open three times between 2002 and 2015, as well as seven Wimbledon titles -- the most recent in 2016.
She also won four Olympic gold medals and became the first tennis player to achieve a grand slam in both singles and doubles, where she played alongside her older sister Venus.
In an interview with Vogue magazine, Williams said she would be focusing on her family and business interests.
"I’ve been reluctant to admit to myself or anyone else that I have to move on from playing tennis," she wrote. "I need to be two feet into tennis or two feet out."
"I have never liked the word retirement. It doesn’t feel like a modern word to me," she added.
"This sport has given me so much. I love to win. I love the battle. I love to entertain."
"I’d like to think that thanks to opportunities afforded to me, women athletes feel that they can be themselves on the court."