The former NFL signal-caller made the statement in an interview with the Lubbock Avalanche-Journal for a story that was published Saturday.
"In the past, probably, is the way I'd characterize it," Manziel told the newspaper about his playing career. "I've finally got to a point where I'm trying to achieve happiness in life, not happiness on the football field.
"I know a lot of people probably want me to come back and play and give it another chance, but I don't know, as far as being a person and figuring out life as a young adult -- trying to make it and figure it out -- if I've ever been in a better place than I'm in right now.
"I can honestly say I'm happy and I'm doing the right things to try and put a smile on my face every day, and that means more to me than going out and grinding on a football field."
Manziel, 27, last played professional football with the Alliance of American Football's Memphis Express in 2019. Before joining the AAF -- which folded midway through its inaugural season -- he played for the Montreal Alouettes of the Canadian Football League. The CFL later barred him from signing with any other team in the league.
The Browns selected Manziel -- who won the 2012 Heisman Trophy as a freshman -- with the No. 22 overall pick in the 2014 NFL Draft out of Texas A&M. After two tumultuous seasons in Cleveland, the team released him in March 2016. Manziel held a 2-6 record as their starter.
"During that time when I got drafted, I didn't put in the time that I needed to be a great player and I don't think my heart was in it," Manziel told the newspaper. "And I think when I went back to Canada, it was the same way. I truly believed and truly thought it was what I wanted to do, and my heart wasn't in it, and it worked out the way it did."
Manziel has had multiple off-the-field issues, including a 2016 domestic assault charge against him in Dallas that was dismissed after he participated in an anger management course and the NFL's substance abuse program. In a Feb. 2018 interview with ABC News, he said he had been diagnosed with bipolar disorder and had stopped drinking.
Manziel, who now lives in Scottsdale, Ariz., told the newspaper that his football career "humbled" him.
"Thank God I did get a chance to be humbled," he said, "because when you think you're at the top of the world, it's a dangerous place."