Michael Ball has told how he grappled with nerves and panic attacks early in his career.
The singer said getting glandular fever in his 20s, while starring in Les Miserables, was partly responsible.
The 56-year-old told The Big Issue: “It left me very tired and debilitated and that starts the demons in your head.
“Suddenly there’s this little voice in your head saying ‘You’re going to get this wrong, you’re going to mess this up and let everyone down’…
“The demons take over. You feel you have to look strong on the outside even if you feel like you’re dying. I was going potty.”
And he told the magazine: “Anyone who’s suffered from panic attacks knows how frightening they are.
“And I was getting them on stage. It came to a point I couldn’t get off the Tube, I was so scared of having an attack.”
But talking about surviving the ordeal, Ball said: “I have far ascended beyond every ambition my 16-year-old self ever had.”
The Big Issue, sold by vendors to lift themselves out of poverty, is available to buy across the UK from Monday for £2.50.