Claire Foy had a "breakdown" when she was 23.
The 'Crown' star has battled with anxiety throughout her life and admits there were times in her early 20s where she couldn't cope with her own mental health.
She said: "When I was 23, I had a breakdown. I didn't sleep or eat for a month. It was awful. My life had changed. I felt overwhelmed. I was on stage at the time and working, and I'd just got a really big job [the lead in the BBC's Little Dorrit]. I just couldn't cope."
However, the 34-year-old actress says the arrival of daughter Ivy Rose three years ago made her realise she needed to "sort her life out".
She added: "Having [Ivy Rose] made me think, 'You need to sort your life out.' I just didn't have to live like that. It was unbearable. I was sick of myself."
Claire split from husband Stephen Campbell Moore earlier this year but the pair are very focused on co-parenting their little girl Ivy.
She shared: "[We're] very much co-parenting. It was always going to be like that, anyway, because I always wanted to go back to work. But there's only one mum, and there's only one dad."
And Claire plans to stop travelling when her daughter starts going to school in September.
She told NET-A-PORTER's weekly digital magazine PorterEdit: "I love traveling, but I don't want to be away from [Ivy Rose]. When she goes to school next September, that's it, it'll mean I'm London-bound."