"For a guy that couldn't stop shooting heroin, smoking crack and guzzling booze this is a truly a miracle," he noted on social media. "No matter what you are struggling with today just know that change is possible and you are worth it. You don't have to be perfect." He added a motto from his Twitter bio: "KEEP GOING."
Adams didn't let the milestone go unnoticed either.
"You should be so proud for everything that has transpired as a result of your strength, faith & persistence with your sobriety," she wrote. "I know I am, because it gave me you! Congrats to you babe! Happy 10."
Another "Bachelor Nation" star, Katie Thurston, was among those who congratulated Clark.
Clark has been open about his struggles in the past, explaining that he became addicted to pain pills after suffering a brain tumor. Alcohol was also a problem, and it ended his first marriage. He addressed the subject with Adams early on in their relationship, and her response is partly why they ended up together.
"She didn't have any direct experience with it, but she definitely had an open mind," Clark said on a January episode of the Whine Down With Jana Kramer podcast, "and she asked all the right questions and some of the ones you hear early on, like, 'Can I drink and then kiss you?' And I'm like, 'Yeah, you're good.'"
In December, during another podcast appearance, this one on Click Bait With Bachelor Nation, Clark said that he first realized Adams had feelings for him when she chose to toast with a non-alcoholic drink after one of the show's rose ceremonies.
"The guy came out with the tray of champagne and there was four champagnes and one apple cider and she looks at him and she goes, 'No, I'm drinking apple cider with him tonight,'" Clark recalled. "And I said, 'What?!' She made the guy go back, get an apple cider while all these people are waiting."
The two are currently living together in New York City.
Meanwhile, another crop of singles are looking for love on Bachelor in Paradise, which is being guest hosted by celebrities including David Spade, following the controversial departure of Chris Harrison.