"I feel really good, I don't feel I'm playing any worse," the 36-year-old hooker added. "I'm really enjoying rugby and part of that might be because I haven't 100 percent made the decision. "But I'm fairly sure it will be, and part of the reason I'm enjoying rugby so much, and I hope playing well, is because there's that weight lifted off."
Best made his debut in 2005 against New Zealand, and has 115 caps, the third most for an Irishman. He became captain in 2016 after Paul O'Connell retired, and has skippered Ireland to its maiden two wins over the All Blacks, and a Six Nations Grand Slam in 2018, just the team's third clean sweep in history.
He toured with the British and Irish Lions twice, and has played in three Rugby World Cups. With coach Joe Schmidt leaving the Irish setup after the Rugby World Cup in Japan from September, the team will have new leadership next year.
"I'm feeling very relaxed now that the body feels that it's happy to go on," Best said. "I'm in a really lucky position at the minute that the way I'm feeling, I can go to the World Cup and be at the top of my game. And for me, the way I'm thinking at the minute, that will be a really good time for me.
"Plus, Joe said he didn't want me to keep going without him."
More AP sports: https://apnews.com/apf-sports and https://twitter.com/AP_Sports