Alesha Dixon said she has been “crippled by fear” and struggled with feeling like an impostor.
The star said she felt she lacked the ability to be given the opportunities enjoyed during her career.
Dixon told the Daily Mirror that from an early age she suffered from self-doubt, and has battled to overcome her fears.
The singer and Britain’s Got Talent judge said it took her years to accept that she deserved her career chances.
She said: “I’ve definitely been crippled by fear.
“At school I was a contradiction. Outwardly, I was a confident, brave individual who went for it and was unafraid.
“But inside, I always had a niggle in my brain, moments of self-doubt which made me question my abilities.”
A winner of Strictly Come Dancing, she felt uneasy being offered a judging role on the show, believing herself to be an incapable impostor.
But Dixon has learned to accept her opportunities, and believes that she deserves the roles she has been chosen for.
She said: “Now I see it as an opportunity to learn rather than it being a negative – the things that are the making of you are the moments when you are most challenged.
“I’ve always had strong instincts which have been a good guide for me, and while I’ve definitely been crippled by fear, I don’t allow that fear to stop me from trying – and that’s the most important thing.”
Dixon left Strictly to take her current role on Britain’s Got Talent.