Finally stood up for myself and set a boundary

My ex has a habit of texting me at like 11pm asking if I can switch weekends because something came up. For 2 years I've been saying yes because I didn't want to be "that guy." Last week she did it AGAIN and I just said no. Cited my own plans (which were legit - friend's birthday).

She got annoyed but I was firm and polite. Turns out the sky didn't fall. She figured it out. Feels weird to not automatically accommodate but also feels necessary. Anyone else struggle with this?