How to stop calling people kid?

I've been in and out of various institutions since I was 16. Some of the institutions called us "students" as opposed to staff but that's dumb so we always just said kids and staff. But recently I went to the adult psych ward, and I kept calling the patients "kids" even though some were like 50. It's really embarrassing to be corrected and probably kinda insulting for some of them to be called a kid. How do I stop?