Dread Mondays? You might be experiencing "identity lag".

On Sunday afternoons, Sarah* feels it creeping in.

The sinking feeling. The irritability. The quiet panic.

She'll scroll aimlessly on her phone, pick pointless fights with her boyfriend, or cry for no obvious reason. Then, she wakes up on Monday and pulls on the work version of herself like a costume.

"I don't know how to describe it other than I can feel myself fading out or changing," she told Mamamia. "Weekend me is fun, a bit chaotic, creative. Weekday me is … beige. She's beige."

Sarah said she often feels like a "cardboard cut-out" version of herself at work, one who fake-laughs and wears structured blazers.

"It might just be the culture there but I feel like that I'm faking it and that I have to leave the fun parts of myself at the door," she said. "I don't really have many work friends. And I talk differently when I'm in office. When I get home, I'm exhausted. Like I've been on stage all day."

Watch: How to become a 'personality hire' at work. Post continues after video.

She used to think this Monday mood shift was just being lazy, or too sensitive. Now, she knows there's a psychological term for it; identity lag.

"Identity lag is when there's a gap between how someone sees themselves on the inside and how that identity shows up on the outside," explained psychologist Dr Marny Lishman.

"For example, the identity that shows up with different people and in different contexts. We show up differently in all the areas of our life, very different to what we're probably like in our PJs at home!"

The shift from "weekend you" to "work you" isn't just annoying, it can be emotionally jarring.

On weekends, we tend to lean into who we really are: relaxed, spontaneous, maybe a little messy or loud or creative.

Then, Monday hits, and we often shape-shift.

"We have likely spent a few days 'being' someone on the weekend and now have to switch back to someone else, the work identity, on a Monday," Dr Lishman said.

"The wider the identity gap between 'weekend you' and 'weekday you', the more likely you are to be a bit off, particularly if 'weekend you' is closer to who you truly are and gives you more positive emotions."

Identity lag impacts how we experience the week. Image: Getty.

For Sarah, this couldn't be more accurate.

"On Saturdays, I wear oversized tees, I paint, I go to the markets and talk sh-t with my boyfriends and friends. I think I'm funny and outgoing. On Mondays, I make awful small talk with my colleagues. If they knew the real me, I think they'd be shocked."

When your Monday identity is wildly different to your weekend self, it can feel like putting on a mask. And, according to Dr Lishman, that can take a real toll on your mental well-being.

"It's almost like we are putting a façade on for certain contexts, thereby being someone we're not. This can get tiring when we're out of alignment with who we truly are. Not feeling authentic can sometimes wear us down, and can also impact our connection to others as we're not being 'real'.

"It could lead to burnout as it's like we're putting on a 'front' and pushing our real feelings aside to help cope with certain situations that might be causing us distress."

And it's not just mental fatigue, it's physical.

"By Thursday, I start fantasising about quitting and starting a ceramics studio," Sarah joked.

According to Dr Lishman, that kind of exhaustion is a common sign of identity lag. Others might find themselves emotionally checked out, feeling unfulfilled by their work, or craving time alone to "reset" every weekend.

"They might feel dissatisfied or even unfulfilled after a week's work because they are out of alignment with who they are and what they truly want to be doing in life."

This misalignment doesn't just mess with your mood, it can tank your focus and motivation, too.

"Focus, mood and motivation can all be impacted by the transition from weekend to work mode, and will be more so the bigger the identity gap," Dr Lishman explained.

"Which means the more different we are on the weekend to the week, the harder it likely will be. We're likely to be less focused, less motivated and have low mood."

So, what can actually help?

Dr Lishman said the first step is self-awareness.

"Make sure you notice those feelings on a Sunday afternoon and Monday morning — what are these feelings telling you? Are they telling you that you need to get a different job? Are they telling you to apply for a different role? Communicate with someone about something? Study to do something you've dreamed about? Listen to those feelings."

For others, it can be more about bringing more of their authentic selves into the working week.

In Sarah's case, she's been "seriously considering changing jobs".

"Somewhere with a culture that actually encourages people to be themselves, not just perform some polished version of who they think they're supposed to be. Because I think we're all a little beige, to be honest. I'm sure my colleagues have lives I don't know about. I'm not special."

*Name has been changed for privacy reasons.

Feature Image: Paramount Pictures.