"I know who I am certainly by 57 now," Stamos said on Wednesday's episode of E! News' Daily Pop.
"It's been close to six years in June that I sobered up," the proud father continued. "I never could have been a father during some of the more - some of it was really fun and some of it got to be very unhealthy."
Stamos was charged with a DUI in June 2015, and checked himself into rehab for a 30-day substance abuse program afterward. The actor married Caitlin McHugh in February 2018, and the couple welcomed Billy that April.
John Stamos Instagram
"Being a parent is about sacrifice. You don't get rewarded for it," Stamos said Wednesday. "You don't get a trophy or a ring, but what you do get is, you get a child who is more loving, more kind and a smarter version of you, and I think that's really special."
John Stamos, son Billy
"I had this beautiful moment last week at Petco's stadium, where he sat on my lap during 'God Only Knows' and it was like a moment that I never thought I would ever have," Stamos told Entertainment Tonight earlier this month. "You know, it was nice."
The Fuller House star previously told PEOPLE that fatherhood is "better than I imagined. I wanted kids my whole life. And I'm just so grateful."
Stamos appears to have passed the acting bug down to the next generation. "We've been watching [comedian] Bill Irwin to learn how to pantomime and tip hats," he told PEOPLE in April.
"Everything's a bit to him," he added of Billy. "He's the most charming kid!"