Actor Brad, who wed the Friends star in 2000 after meeting in 1998, says he was bored and unsatisfied with life when the pair were together.
'I spent the '90s trying to hide out, trying to duck the full celebrity cacophony,' says Brad, 47.
'I started to get sick of myself sitting on a couch, holding a joint, hiding out. It started feeling pathetic.
'It became very clear to me that I was intent on trying to find a movie about an interesting life, but I wasn't living an interesting life myself.'
Brad now has 6 children with long-term partner Angelina Jolie, 36, and has no regrets about ditching Jen, 42.
'I think that my marriage had something to do with it,' he tells US magazine Parade.
'Trying to pretend that marriage was something that it wasn't.'