The biggest regret you will have in your life, according to experts.

There are regrets like not being firmer with your hairdresser when you asked for “just a trim”. And then there are all-consuming regrets that keep you up at night, replaying events in your mind over and over, thinking about what you should have said or done.

But what new research has shown is that it’s the thought that we have not lived up to our potential that is the deepest source of regret for most people. That there was someone that we could have been if we’d only tried harder/taken more risks/been more determined.

Cornell University’s psychologist Tom Gilovich and fellow researcher Shai Davidai found that people were far more “haunted” by failing to reach their goals and fulfil their dreams than by failing to fulfil duties or responsibilities, like missing a deadline or dropping out of a degree.

Not living up to our ideal self

The research paper, The Ideal Road Not Taken broke down people into three versions of ourselves: our actual self, our ought self and our ideal self.

While our actual self is who we believe we are, and the ought self is what we believe other people want us to be, our ideal self is who we want to be – who we wish we were.

The participants were asked questions on these topics and when asked to name their single biggest regret in life above anything else, three-quarters of participants responded with a regret about not fulfilling their ideal self.

While this might all sound, well, kind of depressing, clinical psychologist Samantha Clarke told Mamamia this research finding is actually really positive.

Dr Clarke said that once people identify what they regret, they are also able to identify what changes they could make to their lives from now on to become something closer to their ideal self.

“It’s almost like the feeling of regret is the thing that we need to be some kind of wake up call, to go ‘hang on a second, I’m feeling this, there’s some reason for that’. And looking into it, and using it to motivate you to change your actions,” the Mind Body Resilience creator said.

“It’s never too late. Even if you’re on your death bed there are things you can do to move towards that self that you want to be.

“It’s really about noticing that regret and seeing it as a sign that you’re not where you want to be… it’s a really good thing to acknowledge that regret.”

Dr Clarke said people not living the life they want was something she saw all the time in her patients and in workshops that she ran. Often, she said, fear was holding people back.

“It’s really common. There’s a lot of fear that often goes with taking that risk to really move towards what you really care about. And this idea that when we move towards something we really want, we’re scared of that because we think ‘what if I don’t achieve it? What if I fail?'”

She also said people might not even realise this regret is a root cause of bigger problems – or even the best way to motivate better mental health.

“People come in for sessions about something else, but as time goes on and we’re exploring things what comes out is that they’re actually not moving towards something that they’re really passionate about.”

“And often when we find that, that can often be the motivator for then do the other things to get well.”

Turning regret into a motivator

If you’re reading this thinking this unlived life might be bothering you, Dr Clarke suggests trying to identify exactly what it is you want to do or be – a journal can help – and then figuring out what you can do to get closer to your ideal self.

The authors behind the research, published in journal Emotion, said that regrets around not becoming the best version of ourselves could also be more widespread because they represent vague, unachieved goals.

For instance, being a good parent. “Well, what does that mean, really?” Gilovich told the Cornell Chronicle. “There aren’t clear guideposts. And you can always do more.”

His major takeaway? If there’s something in life you want, go after it.

“As the Nike slogan says: ‘Just do it.'”