The average adult has six moments of self-doubt a day - including whether they are good at their job.
A poll of 2,000 people found the biggest doubts relate to their work life - with 14% also concerned about their ability to climb the career ladder.
Another 25% have doubts about themselves and lack self-confidence, while 23% worry about whether they are making the right choices in life.
More than a third (34%) also think about whether they will achieve the personal and career goals they have set themselves for the future.
It also emerged those aged 18-24 doubt themselves most often - eight times-a-day on average.
But those aged 65 and over feel most self-assured - only feeling self-doubt five times-a-day.
The study was commissioned by Cadbury, which has partnered with the Prince's Trust to launch its 'Give a Doubt' campaign - which hopes to increase self-confidence in younger people by encouraging the public to share their own self-doubts.
The hub will offer support, advice, and guidance from The Prince’s Trust, giving young people the tools to help them overcome their self-doubt and thrive in their personal and professional lives.
Michael Moore, a spokesperson from Cadbury, said: “Through the ‘Give a Doubt’ campaign, we want to get everyone sharing their own doubts, starting a conversation to show that day-to-day uncertainties are normal, and that we all experience them.
“Helping young people to realise that these uncertainties needn’t hold them back and sharing a doubt can help to overcome theirs and restore their hopes for the future.
"Sharing a doubt of your own is an act of generosity, that will help young people nationwide to feel more confident about their futures."
The study also found just 22% of those, aged 18 to 24, have feelings of self-confidence at the moment, compared to 53% of adults aged 65 and older.
However, the age of 28 was revealed as the turning point - when people first start to get that feeling of self-assurance.
It also emerged only 26%, polled via OnePoll, will speak to others about feelings of self-doubt, with others preferring to solve their problems alone, not wanting to bother other people or appear ‘weak’.
Jonathan Townsend, UK chief executive of The Prince’s Trust, said: “Self-doubt and lack of opportunity should not hold young people back from having thriving, positive futures.
“We help young people into jobs and training, and we know that with the right opportunities and self-belief, every young person, no matter what adversity they face, can succeed and achieve their goals in life.”
The partnership also sees the launch of special limited-edition packs of Cadbury Dairy Milk bars, displaying the doubts of footballing legends Ian Wright, Steph Houghton and Gary Neville.
Former Arsenal striker, Ian Wright, said: “We all have doubts. I didn’t think I’d ever make anything of myself.
"I doubted whether I could become a footballer, doubted whether I could work in TV.
“Then when I started working in TV, doubted whether I’d be there for long. I wasn’t TV trained, didn’t finish school, but there I was hosting a prime-time gameshow for millions of people.
"Everyone has doubts, but over time I have gotten better at managing them and trying to make sure they don't stop me from doing the things I want.”
Former Manchester United and England international Gary Neville added: “I can definitely relate to having moments of doubt.
"It happened to me when I was playing during a European Quarter Final, I didn’t want the ball, my belief went.
“This is why I'm so proud to be part of this campaign which aims to normalise these moments of self-doubt and empower young people to overcome them.”
BRITS' TOP 10 BIGGEST DOUBTS IN LIFE:
- Lacking in self-confidence
- Having the confidence to make the right life choices
- Losing the confidence you had when you were younger
- Lacking the confidence to stay in touch with friends and family
- If you are good enough at work
- Whether you're confident enough to speak up
- Whether you're confident enough to make friends
- Whether you have the confidence to change career paths
- If you have the confidence to climb the career ladder
- If you'll be successful in your career
