Good for you. You handled that nicely.
For anxiety and people pleasing, it can be helpful to have a default answer. You know, the thing you blurt out when you are like a rabbit in the headlights. Your default seems to currently be "Um, OK", which isn't helping you.
How about these instead: "Why do you ask?" "Why?" "Why not?" "Oh that's a shame" "Oh, poor you" "Oh dear, what are you going to do about that?" "I wouldn't be comfortable with that."
If comes out nervously because you are anxious it still works. Mildly and casually is the best way though (not aggressive).
Do you always get the early train? "Why do you ask?"
My child was late for school "Oh that's a shame"
Are you going to my school? "Why do you ask?"
Can you take my child with you? "Why do you ask?"
I can't take my child to school because I have work meetings this morning "Oh dear, what are you going to do about that?"
I want you to fix my mistake "I wouldn't be comfortable with that. I hope you find a way to get it sorted. Bye."
It gives you time to think. It makes it much easier to work yourself up to saying "No" or saying "Yes" and feeling good about saying yes.
Happy birthday.