"I thought I'd helped my friend through her break-up. Then she opened her computer."

I spent last Thursday night on the floor of a living room, sandwiched between used tissues, Instagram feeds and dirty plates.

I was playing psychologist to a friend who had recently ended things with a boyfriend we jokingly referred to as “Baby Tom”.

Baby Tom and Sarah* had lived together for four years.

In this time, his biggest achievements could be counted on the screen of a Playstation menu, where he listed his name as “Baby”. He was a sweet guy but spending time with him was like hanging out with a sleepy Labrador.

Baby Tom was dumped a little after Christmas. Sarah said she couldn’t see a future with a man who was so happy to coast and Baby Tom said very little.

Searching for love advice? Listen to hosts Osher Gunsberg and psychologist Leanne Hall on the Love Life podcast.

Fast forward three months and Baby Tom’s face beams only from the white light of Sarah’s laptop screen.

“I can’t believe it,” she said. “What a joke.”

In the short time the pair had been apart, Baby Tom had undergone some kind of “12 Week Life Transformation.” He’s employed. He’s socialising. He’s filling his Instagram with days at the beach and women we’ve never seen.

This is no post-break up haircut. This is a 12 week life transformation.

“I REGRET EVERYTHING,” Sarah cried.

I tried to soothe her but regret is a powerful feeling, and one that is all too commonly linked to lost love.

In 2011, a study at Northwestern University and the University of Illinois at Urbana-Champaign asked 370 Americans to describe one significant moment of regret.

The majority of respondents recalled romantic decisions, followed by family, education, career, finance and so on.

Co-author and Kellogg School of Management marketing Professor Neal J. Roese said such feelings were only natural.

“Regret is an essential part of the human experience—something everybody has as long as they have life goals,” he said.

“Rather than avoid it, it’s better to try to take some insights out of the regret experience.”

These were not the ideas I shared that evening but they do offer hope and a perhaps an explanation into how Baby Tom was able to kick his life into gear so quickly.

It's unclear if being dumped by Sarah caused Baby Tom to realise he regretted his current life enough to make a change but the idea isn't too far fetched.

The feeling of regret is often classified as a "negative emotion". It fosters feelings within the individual that things would have been better if a different course of action had been taken.

But as Professor Roese said, regret for past mistakes can inspire positive choices, too. Regret can be a driving force, using past situations as a guide in "what not to do".

Sarah now tells me she only wishes she could have experienced his transformation firsthand.

She is comforted by his new life and only regrets not having ended things sooner - not for her progress, but for his.

The pair remain separate.

*Names changed.

Have you ever used past regret to make better future choices? Share your stories below.