I should note that I'm also in the UK.

I've definitely met people who haven't been able to leave their work behind when on holiday. I've not worked anywhere where that's a majority, but as a minority they were obviously more noticed for it, especially when they were sending emails at 5am or from a beach somewhere.

They would reject the advice that they should just stop working sometimes, they saw themselves as too important and too critical to the business. They imagined that if they didn't respond to an email the same day they received it that the business would fall apart.

This isn't the case of course, but they lived in fear that they'd "let the company down", or that things would fall apart without them being always available, but they never let that actually be tested.

One infamous colleague was rumoured to be replying to business emails on their honeymoon. ( Probably just a rumour. I hope. )

Indeed, had they tested it, they'd have likely discovered that they would get away with being on holiday without responding. Indeed even that having work/life boundaries are actually seen as a positive thing not a detriment.

I found myself suddenly taking 14 months off work from zero notice due to my health. Despite the fact I thought myself as fairly important to the development team at that time, but did the business fall apart? No, it just got on with adapting to the new reality and my absence was barely felt.

It can be uncomfortable for some, but the business will manage without you. Indeed if it couldn't, then that's a critical failure point that should be optimised out. You're also preventing yourself from being promoted if you've put the business in a situation where literally no-one else can fill your role.

I find I get frustrated when people don't test limits nearly enough, especially when those limits are either imagined or due to too much deference to the concept of "the business" as some kind of entity that must be pleased.

People will work long hours, or work their weekends so that they never miss a deadline, but have never tested to see what happens if that deadline gets missed. The reality might be that they actually get more resource to do it in time, rather than the imagined reality of disaster for everyone.

Especially in the UK with good employment laws, there is never a case where someone could be dismissed for not working their weekends. It almost surely would be unfair dismissal, and companies know this. But that doesn't stop inexperienced workers from half-killing themselves to get something done.

And that stress can bleed into their interactions with other colleagues, no just because overworking increases stress generally, but because they will often see colleagues who refuse to sacrifice their free time as "lazy", further increasing hostility.

Becoming trapped by the imagined result from saying "no" or setting boundaries causes those walls to grow higher, as norms in relationships are set around crazy hours or never saying no, increasing the size of the perceived disaster to finally saying no.

Eventually this often leads to burnout or worse, finally snapping and unreasonably shutting down completely in what used to be termed a "nervous breakdown" although I suspect that term isn't the current one.

I've learned to set expectations early, even signalling in interview, that I will not be that kind of person. That I'm comfortable setting boundaries and comfortable with challenging people who over-work.