The 36-year-old revealed she simply “couldn’t continue” after her father, Colin, 80, lost his battle with cancer but “hated” letting the audience down.
Appearing on Saturday’s Jonathan Ross Show, the actress spoke about how hard it was taking time out.
She said: “It was the worst thing, I hate it and I always think ‘The show must go on’ and I hate letting anyone down but I think the public understood in a way that you can’t choose when these things happen.
“It was a gradual build up when my dad got diagnosed and I just couldn’t continue, I lost my mind, I completely did to the point where people were stopping me in the street and cuddling me because people understand that, it’s just life.
“Unfortunately you can’t just take time off from a show, you get a lot of abuse so that’s what happened.”
Sheridan also opened up about her battle with her mental health and said her father’s death and diagnosis was the “catalyst”.
She continued: “I’d been performing anyway leading up to that, and I’ve always had a bit of anxiety, and so I was a little bit nervous but the catalyst of it all was my dad.”
The Gavin and Stacey star revealed she is now in a “better place” and urged people to speak out about their own struggles.
“Now I’m in a better place, I want to say ‘It’s okay not to be okay’ because I didn’t speak about it and then it snowballed and it came to this huge head.
“You’re scared to ask for help because people think ‘Oh what have you got to be worried about?’ and I get it but I just think, if [me speaking out] helps one person. I’ve had a lot of messages from young girls. I hope it helps.
Sheridan is joined on the chat show by comedian Peter Katy, actor Luke Evans and voice of Love Island Ian Stirling.
The Jonathan Ross show airs tomorrow on ITV at 9.40pm.