Setting boundaries is possibly the hardest but the most rewarding thing to do. When you are managing people it’s very easy to fall into the “always on” trap. Your team need to be able to access you but that doesn’t mean they get to interrupt you throughout the day and expect you to work to their time frame. Set regular interruption points throughout the day and communicate that to your team.
This works for managing up too. You don’t have to accept everything that comes down the chain to you from your line manager or those more senior than you. The trick is how to say no without causing offence. One trick I use is to put it into context of something else that has to give; “I can do that but x project will be delayed as a result” or “I can do that but not until next week”.
Your time is precious and you are the only one that can control what dominates your time.