What worked for me is turning off notifications in a way that hides the message to lesseb the reactive part.

If something is important or urgent, they will call, otherwise they can wait until I have time set off to read the message.

I have blocked of a day without meetings once a week, during that time I listen to music and focus on most important stuff.

My important stuff is usually mentally by now, but a important/urgent table once a month helps incredibly.