Alan Robertson and Lisa Robertson are discussing a difficult time in their lives.

The Duck Dynasty stars detailed how they worked through an affair Lisa had 15 years into their marriage, a chapter of their decades-long relationship that’s chronicled in the upcoming movie Faith & Forgiveness.

“When unfaithfulness happens in a marriage, so many times, that’s the end of it, but it doesn’t have to be,” Alan shared with Fox News Digital in an interview published May 15. “Everything can be worked through.”

Lisa—who married Alan in 1984 and shares daughters Anna and Alex—had an affair with an old boyfriend in the 1990s. And although the couple agreed to a temporary separation when Alan found out, they ultimately reconciled and renewed their vows in 1999.

“I think the reason I was willing to fight for my marriage was that I had made a lot of mistakes on my own,” Alan explained. “When I first met Lisa, she was actually a good girl, who had experienced some hard things in her life up until that point, but really was looking for what she called her ‘knight in shining armor,’ someone to take her hand and lead her out of some things. And I just wasn’t that guy in the early years.”