It has been found that 85% of people aged over 50 think they retired too early, with this number rising to 88% among those who are now older than 70.
That is according to the findings of a survey by SunLife, released today, which reveal that, on average, those that are retired or semi-retired think they did so two-and-a-half years too early.
This rises to three years too early among people aged over 70, with less than 10% thinking they retired too late, and just 5% believe they got the timing right.
"Our research shows that people aged 50 and over feel 10 years younger mentally and almost four years younger physically," SunLife marketing director, Ian Atkinson, said.
"So, far from being 'over the hill', people in their 50s, 60s and 70s are feeling fit, healthy and sharp, which could explain why so many feel they gave up work too early and why so many are starting new careers."
There were 50,000 over 50s who responded to the SunLife survey, which is believed to be the biggest-ever research project into this age group.
The findings show that a fifth of retirees are earning money in alternative ways, with thousands starting their own business, and 18% doing things like selling items on ebay or private tutoring for an income.
"Many people in their 50s, 60s and 70s have made big changes in their work lives, by either dropping to part-time, or giving up stressful careers to do something they are more passionate about," Atkinson continued. "Far from being the end of working life, for many, turning 50 actually offers a brand new start."
This comes after previous SunLife research revealed that 62% of over 50s believe they have missed out on a job because of age discrimination, and 5% think they have been encouraged, or forced to retire.
With the UK's ageing workforce getting larger, and pressure on the pensions system increasing, there are calls for companies to recognise the value in older workers.
"50 is definitely not old, and with life expectancy and retirement age rising year-on-year, life after 50 certainly doesn't mean the need to slow down or take it easy - and more businesses need to realise that," Atkinson added.