'After 5 years of mixed messages, my commitment-phobic ex settled down... with someone else.'

You know that gut-punch moment when you find out your ex — the one who spent years telling you he "just wasn't ready" for marriage and kids — is now living his best #DadLife on Instagram with someone else?

Yeah, we need to talk about that.

It's just like Miranda once said in Sex and the City… "Men are like cabs."

What she meant was, that like a cab, a man's "available" light switches on and off. When they're off, nothing is going to make them stop for you. But when that light flicks on? They're suddenly racing down the aisle with whoever happened to be standing on the corner at the right time.

Watch: The Taxi Light Theory on 'Sex and The City'. Post continues after video.

Two decades later, this theory is having a renaissance on TikTok as women share their own taxi light horror stories. But none quite hit home like Sarah's*.

Sarah spent around five years in an on-again, off-again situationship with Adam*. A guy who couldn't even commit to a gym (her words, not mine). They met when she was 25, he was 30, and what followed was half a decade of what she calls "mixed signals, half-promises, and me convincing myself that he was committed, just in his own way".

"He'd tell me straight up, 'I just don't see myself settling down' and 'I love you, but I don't think I'm husband material,'" Sarah told Mamamia. "And he never gave me a straight answer about kids, which he knew I wanted.

"But he would act like my boyfriend and talk about our future in these vague ways. Just enough to keep me hooked."

As she approached her 30s, Sarah's biological clock was echoing louder in her ear, and she was done playing the waiting game. She gave Adam an ultimatum: either we move forward, or I'm out.

"He basically let me go without even fighting for us," she recalled. "He was like, 'I love you, but I can't give you what you want.' The most humiliating part is that I thought he would beg me to stay. It was really eye-opening, in the worst way possible."

Not even two years later, Sarah was scrolling through Instagram and there it was. An announcement she never thought Adam would make.

"She said yes," read her ex's post, his fiancée beaming down the camera as she showed off the diamond on her left ring finger.

The guy who "wasn't wired" for marriage was headed for the aisle.

"I think I was in denial for a few days," Sarah told us of her reaction.

"But when it finally sank in, I sobbed, and then I laughed, and then sobbed and sobbed and didn't stop. I wasn't really mourning the relationship anymore, I just felt so small. He kept saying he was the reason he couldn't commit, but clearly it was me."

At the time of the engagement announcement, Adam was in his late 30s. And while men don't have a biological clock, Sarah definitely thinks a timer was going off in his head.

"He didn't change because he met the 'right person'. He changed because he decided it was time," shared Sarah. "At least, that's what I think."

About a year after the wedding, Adam and his wife welcomed their first child. It was another punch to Sarah, who had been vocal in her desire for kids during their relationship.

"Men can wake up at 40, 45, even 50 and decide they're finally ready for children with zero consequences," Sarah pointed out. "But I felt so much pressure to be pregnant by my early 30s, otherwise I would miss my chance."

With similar stories popping up on TikTok, I was curious to see if this Taxi Light Theory held any validity whatsoever.

And Psychologist Carly Dober says no… not really.

@milamagicccc She just started closing her eyes and waiving her finger @Aiah 🤣#fyp #viral ♬ original sound - Milamagic

"This is not a psychological term," she told Mamamia.

"I don't actually think true signs of settling down differ between sexes or genders. I think when people are ready to settle down, they approach relationships maturely [and] openly; they can communicate honestly and clearly about what they want; their behaviour matches their words; they integrate you into their life, and they discuss their future with you."

In Sarah's case, Adam would discuss their future but in vague terms — what she now knows to be "future faking".

But if the Taxi Light Theory is just that — a silly little viral theory — why is it happening to so many people?

"When there is a mismatch between how much we like someone versus how much they like us, or where we see them in our lives versus how they see us in their life, we search for answers because we want closure," said Dober.

"This experience can be quite painful, and I think people connecting through their heartache and confusion can be a helpful thing."

Instead of the Taxi analogy, Dober suggests the metaphor of "growing a garden".

"Those who mightn't be ready just want to walk through and enjoy the colours and scents, those who are looking for something short-term might have a picnic there, and those ready for a long-term commitment will be planting seeds to nurture them over the years."

Luckily, Sarah's garden has since flourished, and her story has a happy ending. After Adam, Sarah found the love of her life and started the family she had dreamed of for years.

"He wanted to be with me, and that was it. No games, no hesitation. I just wish I met him earlier, but timing is everything."

As she moves further away from her past, Sarah's understanding of the Taxi Light Theory has certainly evolved, but not entirely.

"I think it's not that men have some internal switch that suddenly flips. It's that when someone is truly ready, their actions align with their words," she said.

"There's no confusion, no mixed signals. And that readiness has nothing to do with the woman standing in front of them — it's about them.

"I still think the Taxi Light Theory holds weight in terms of how many women have experienced it. But I also think we should be focusing on whether we're choosing people who are actually showing up fully from the start."

*Names have been changed for privacy. The feature image is a stock photo and does not represent any of the people in this article.

Feature Image: Getty