You put a case on your phone and a lock on your bike. What’s protecting your time?

You already understand protection when the thing is physical and replaceable. Time gets no such treatment, even though it is the one resource that does not come back, and it leaks in small amounts to whoever asks first. Nobody takes it dramatically; it goes in fifteen-minute pieces you agreed to.

Find the two or three places your week actually drains into and put something in the way: a fixed finish time, a blocked hour, an answer decided in advance. Treat one block each week as unavailable. You owe no more explanation for that than you do for locking a bike.