How can I learn from other people’s mistakes? What do retirees wish they had done differently?

A survey showed the following:

53% of retirees say that ‘Start saving at an early age’ is the best financial advice they have ever received.
Younger workers expect to retire earlier than older workers: on average, those aged 25 to 34 think they will stop working at age 58, while those aged 45 to 54 see themselves retiring at age 63. It is only when people pass the age of 55 that their expected retirement age jumps to 65 [because they are not prepared].
64% of semi-retirees wish they had worked full-time for longer.
For the next generation of retirees, retirement savings are expected to last 10 years, indicating a belief among today’s workers that they are less well prepared.
63% of retirees worry that they do not have enough money to live on in retirement, and 70% of those people regret not saving more.
Only26% of retirees have used a professional financial adviser.
Retirees say the following is the best advice received, in order of importance:
Start saving at an early age
Start saving a small amount, regularly
Don’t spend what you don’t have
Buy your own home as soon as you can afford to
Buy only what you need
Develop a financial plan for the future
Source: HSBC study: The Future of Retirement – Life after work?