Shia LaBeouf and Carey Mulligan split because of incompatible "lifestyles".
The 26-year-old actor dated his 'Wall Street: Money Never Sleeps' co-star for just over a year until October 2010 and though they were smitten when they got together, LaBeouf doesn't think their relationship would have lasted because they were such different people.
He said: "Carey is not just an actress, she is a great human being, a sweet girl and super intelligent. Our thing came down to not having compatible work/lifestyles.
"We were always travelling, and had sensibility differences that weren't conducive to living with one another.
"I'm harder on myself and my surroundings than she is, and we had a culture shock in terms of meeting her parents and vice versa. Sensibilities, cultures, histories. There were differences, that's all."
In April, Mulligan married singer Marcus Mumford and LaBeouf thinks he makes the actress happier than he could ever have done.
He told the Sunday Times magazine: "She's happy as hell right now, and we wouldn't have been able to make it like that. She was chasing marriage, family, kids more than I was."
LaBeouf - who is currently dating fashion designer Karolyn Pho - hopes to marry himself one day but won't rush into settling down as he plans to tie the knot for life.
He added: "I'm not opposed to marriage. I just think I'm quite young. I come from divorce. I'm only doing marriage once. It's not a game for me. I'm not a religious person, but I have ethics."