Billy Bob Thornton Admits He "Blew It" With Ex Angelina Jolie: "I Wasn't Good Enough for Her"

In a candid new interview with ABC's Nightline, Angelina Jolie's ex-husband Billy Bob Thornton opens up about his marriage to the superstar and how he "blew it." 

Although Billy Bob admits that he and Angelina are still "good friends," he reveals that he was the reason why their three-year relationship — which lasted from 2000 to 2003 — ended in divorce. 

OK! GALLERY: ANGELINA JOLIE STEPS OUT WITH BRAND NEW ENGAGEMENT RING IN L.A. 

"We had a great time together," Billy Bob tells Nightline in an interview airing tonight at 11:35 p.m. on ABC. "We had a great marriage, and I chickened out because I didn't feel good enough.

"I didn't think I was good enough for her," he added of the actress, who is now engaged to longtime love and the father of her six children, Brad Pitt. "She has one way she wanted to live her life, and I had another way to live mine and I was just too insecure."

Billy Bob confesses that he "did feel like the Phantom of the Opera hiding in the catacombs" during his marriage to Angelina and was affected by people's hurtful comments.

"People have actually said that I didn't deserve to be with her," Billy Bob explains. 

"When you're in a relationship, any two celebrities or whatever, you know, I think that puts on a lot of pressure," he continues. "When Angie and I got married, during that time, I was more famous than she was to start with and then she becomes this big thing, it's hard in these relationships."

OK! GALLERY: BRAD PITT & ANGELINA JOLIE ARE ENGAGED! CHECK OUT THEIR BEST PHOTOS THROUGH THE YEARS! 

But despite all the speculation surrounding their odd romance, Billy Bob insists it was his insecurity that ended the marriage.

"That's all that happened. It was no big deal," he says, "we never hated each other."