Williams made the comment after beating Elina Svitolina in straight sets in a women's singles semifinal matchup Thursday in Forest Hills, N.Y. She is vying for her record-tying 24th Grand Slam title.
Williams also set a record for the longest gap between Grand Slam final appearances, with her first Grand Slam appearance coming at the 1999 U.S. Open.
The six-time U.S. Open champion hasn't won the Grand Slam since 2014. She lost in straight sets to Simona Halep in the 2019 Wimbledon final. She was knocked out in the third round of the 2019 French Open. Karolina Pliskova bounced Williams in the 2019 Australian Open quarterfinals.
World No. 1 Naomi Osaka beat Williams in straight sets in the 2018 U.S. Open final.
"I felt more prepared this tournament," Williams said. "Wimbledon, I probably had a week to prepare so that was amazing. Australia I was super prepared and did great and rolled my ankle. I shouldn't have even played the French Open, so that was a bonus just to compete in another Grand Slam.
"I just feel like I actually had time to train. I joked that I trained more for Canada than I did for any other tournament this year."
Williams reached the final of the Rogers Cup in Canada before retiring in the first set of the match against Bianca Andreescu. She also pulled out of the Cincinnati Masters due to back issues before the U.S. Open.
"I just had a really tough year with injuries and mostly bad luck," Williams said. "I just needed to get injury free."
Williams said she still would be playing even if she already passed Margaret Court's record of 24 Grand Slam victories. She said she put in a lot of gym time and focused on her fitness following her loss at Wimbledon.
Andreescu and Williams match up once again for the 2019 U.S. Open women's singles final at 4 p.m. EDT Saturday. Andreescu, 19, is the second Canadian woman to reach a Grand Slam final.
"She really knows how to mix up the game and play different shots in different ways," Williams said of Andreescu. "Above all, I just like her as a person. She's amazing."