Time blocks look perfect on Sunday and are wrecked by 10am on Tuesday Planning

You're planning a week that has no room in it. Three changes, in order of how much they'll help:

Block at most 60% of your available hours. If you have eight working hours, that's about five blocked and three genuinely open. The open time isn't slack you're wasting, it's where the urgent thing goes. When you block 100%, one interruption doesn't cost you an hour, it costs you the whole plan, because everything after it is now wrong.

Plan Sunday in themes, not in specific tasks. Tuesday morning is writing, Wednesday afternoon is admin. Decide the actual task on the morning, when you know what happened Monday.

Add a five minute replan at noon every day. That's what turns the plan from a fragile artefact into a moving one, and it's the step everybody skips.

For a genuinely reactive job I'd go further and block one thing a day, not a week of blocks. One 90 minute protected slot in the morning for the work that only you can do, and the rest of the day is fair game for whatever arrives. I've kept that for three years, which is longer than any full system I ever tried.

Also stop rebuilding the plan when it breaks. A wrecked Tuesday doesn't invalidate Thursday's blocks. The move is to drop today's remaining blocks and keep the rest of the week, not to declare the whole thing dead and freewheel until Sunday.

Track for one week what actually interrupts you and how long it takes. Most people discover it's the same two or three recurring things, and those can be scheduled rather than absorbed. My plan stopped breaking when I realised the interruption was always a specific colleague on a specific day and I just gave that a slot.