These troubles culminated in a reckless driving conviction in 2015, but Cassidy assures ET that he's now sober and back at work.
"I still have a job to do," says Cassidy, who is currently on tour across the U.S. through next year. "That makes me want to continue to inspire people."
Cassidy says he feels "grateful" that he now has his disease "under control."
In addition to hitting the road, Cassidy has also been hitting the studio. His new collection of Christmas songs, A DC Xmas, is available now at www.davidcassidymusic.com, and he opened up about finally doing a holiday project.
"Fans have asked me to do it, but it was like I was doing something else. It's like, 'Yeah, I'll do it someday,'" Cassidy says. "Well someday has come and it's so great. There is an original song on it also and it is such a great thrill for me to play and work with musicians. I get to work with the best in the world, and they are like my second family. We travel around the world now. They are off the hook!"