The Skyscraper singer realised she needed to get help after she punched her backing dancer.
The 18-year-old star checked into a treatment centre, where she received help for depression and an eating disorder, in October after an altercation with Alex Welch - and says she had been 'out of line' for months beforehand.
She said: 'I was completely out of line all summer. Just the worst attitude - totally ungrateful. I just felt like she had betrayed me. That's the bottom line. When you punch someone on a plane, enough is enough. Right after, I texted my mum and just said, 'I'm sorry.''
But Lovato says her problems weren't caused by her split from Jonas Brothers star Joe Jonas.
She added to US Elle magazine: 'I wouldn't credit my meltdown to a guy. There was so much other stuff in my life.'