I worked hard to break that habit in myself. My workplace (telco) gives all employees a phone and home internet, both with unlimited subscription, 100% free for private use as well, and a cable TV package if we want it. The purpose is that we can work from home as necessary, and obviously also act as brand ambassadors. Our phones are eligible for replacement every 3 years or so, for free.

For a lot of my colleagues, this is their only phone, because why wouldn't it be? Many of them habitually check their work email all the damn time, and I can see them online in Skype for Business, even when they're on vacation. I used to do that as well, compounded by a manager who expected to be able to reach us at any time.

So I bought a phone and personal subscription for myself, and most days I leave the laptop and work phone in my locker at work. Now when I'm off work, I'm off work, period.

A few trusted colleagues have my unlisted personal phone number, in case of serious emergencies only, but they haven't had to use it yet.

As for what to do with yourself, you need a hobby :-) Something completely unrelated to work, like bicycling or video games or woodworking. Something you do for yourself and/or your family.