Bordeaux striker Carroll was one of the club’s most expensive ever signings when he joined in January 2011.
However, he was not able to shine, and was eventually loaned and then sold to West Ham.
“It was a really tough time in my life, really,” the 35-year-old told Foot Mercato.
“It was a stressful time for me. I was down in the dumps, everything was dark. It was hard to get back up. I was just falling apart and making bad decisions and mistreatment and bad things. It was just really tough.
“As a player, you just want to be out there and playing. But sometimes you hear stories, people saying, 'oh, he's still injured', 'he should retire' and things like that that are not nice.
“At that point, you're in a hole, in your shell and you're just trying to get out of it, because it can be dangerous. Luckily, I managed to get out of it and I had a more positive ending. So now I just love playing football.”