The brunette presents spin-off show The Xtra Factor in the U.K., which goes out live immediately after the main programme and involves interviewing contestants who have just been kicked out of the contest.
Flack, who reportedly dated The X Factor contestant and One Direction star Harry Styles in 2011, found the emotional job too stressful and ended up having professional counselling to help her cope.
She tells British newspaper the Daily Mirror, "Sometimes you get caught up in your own mind - especially in this job - and you just need someone to snap you out of it and go 'Come on!'
"It was all manner of things which just built up - work stresses, life stresses, family stresses and relationship stresses. Talking to someone just helps as a problem shared is a problem halved. I loved it and to be honest it got me through quite a lot... I'm very happy now."