Monday Hour One

I have a busy job with multiple roles and projects and frequent interruptions. I often need to put in many hours supporting people to meet urgent deadlines. I have been trying to implement Monday Hour One (in my case Sunday Hour One) but am finding it very hard to stick to it because of the amount to do (i.e. multiple serious projects with deadlines coming up soon, days with many meetings) and difficulty anticipating what will be raised with me. Although I understand that overwhelm is a choice I am making, I still find myself making it often. Because my work spills over into my own time, it also affects other things I want to do.
Are there ways you can suggest I modify my approach to Monday Hour One or start to think about this? Would it help to somehow implement it on a daily basis? I would like my results to be that I finish work at a reasonable time and find it manageable.