When people dwell on regrets and find themselves endlessly brooding and focusing on them, they can become depressed – and often very anxious.
They suffer from low moods and experience common stress symptoms, such as a racing heartbeat, sweaty hands, tension headaches, acidic stomach and insomnia.
A study by Dr Jos Brosschot at Leiden University in Holland showed that a specific kind of stress, known as rumination - or the tendency to brood over events for hours or days after, or worry about them before they have even happened - is particularly detrimental to health.
It’s a condition most often seen in young people, as another study has found that our regrets bother us less as we get older.
Researchers from the University Medical Centre in Hamburg observed and brain-scanned 60 adults, aged between 25 and 65, as they performed tasks involving risk-taking and disappointment.
The team concluded that by the time we get to 65, we have fewer regrets, are more philosophical and are less likely to mull over "what might have been."
This doesn’t mean we shouldn’t regret things - in small doses, it is healthy to. We learn from mistakes and vow not to repeat them.
University of Georgia psychology professors Leonard Martin and Abraham Tesser claim, "Rumination can yield benefits if it focuses on correcting errors and goal attainment."
But being laden with regret is bad for us and can increase the risk of various stress-related illnesses - including heart disease - if not nipped in the bud.
So can you learn to deal with regrets more effectively before you reach 65?
Yes, you can. I tell patients suffering from stress and depression - and fixated on past events or wrongdoing they have committed- to stop castigating themselves.
Try saying, "That was then, and now is now. I did what I thought was right at the time, even if now I regret it." It helps to say it out loud to yourself.
"Physical relaxation techniques may work. And mindfulness therapy, a treatment that incorporates meditation techniques, has been shown to help break the cycle of worry by bringing about changes in the neurological pathways.
"Forms of this treatment are available on the NHS.
"If you have regrets about bad habits you can’t seem to control -such as smoking or drinking too much - it helps to say, "I don’t like my behaviour.
"But that does not make me a bad person. I can change."
Studies show that no matter at what point you give up bad habits, you are likely to improve your health.
It may sound twee, but if you feel upset and guilty about hurting others, admit to your wrongs and apologise for them.
If your regrets fill you with shame, write a list of them on a piece of paper, then tear it up and bin it.
This will help you let go of the regret and feel calmer. Many therapists use this technique, not just for regret but for situations such as getting over a relationship split.
And if you normally keep your regrets to yourself, confide them to someone you can trust. Talking helps lessen the power worry has over us.
Some regrets are to do with events outside our control. We may regret that a partner dumped us, or that we didn’t get that job we wanted, or that someone we thought was a friend treated us unfairly.
We may even bitterly regret the sort of upbringing we had. The truth is that no amount of regretting can alter that past. But dwelling on it can hold us back and ruin the future.
Katie Piper, a beautiful young model and TV presenter, could have been excused for being bitterly regretful after a man attacked her with a cupful of acid, leaving her disfigured.
Instead, she vowed not to be defined as ‘the girl who had acid thrown in her face’ but as a person with a lifetime ahead of her.
Doctors have been responsible for her remarkable physical reconstruction - but she took charge of her emotional recovery.
Now she has started her own charity foundation to help other people who have been badly burned and scarred.
She has turned a hideous situation into a positive one.
And if she can overcome regrets about such a terrible tragedy, you can learn to put your regrets behind you too.
Finally, let me mention the sort of regrets that concern things you wish you had done, as opposed to those you wish you hadn’t.
These – all about our failure to seize opportunities or realise our potential – do not diminish with age. Quite the reverse.
It is these regrets that come to the fore in older people when they receive bad news about their own health or that of a loved one.
A growing number of clients feel panic-stricken about the onset of serious illness and it’s because they feel they haven’t lived life to the full.
If you received a terminal diagnosis tomorrow, wouldn’t it be amazing to say, "I hope I don’t die yet but if I do, I’ve had a fulfilled life?"
It’s never too late to start working towards achieving goals.
As Frank Sinatra said in My Way, you may still have regrets, but hopefully they’ll be "too few to mention."
–Daily Mail, London