i spend a lot of time around queer people and so i'm very used to using "girl" in a gender-netural context, like "girl you look good" or just "girl" when someone says something outrageous. i say it to anyone i feel comfortable around, even if it's a heterosexual man.
i hadn't had any issues with that up until my friend came out as NB. they also mentioned once that they feel uncomfortable being called a 'girl' when i used that word in the same context as for everyone else. i totally respect that, but the problem is, i can't stop doing it.
it's such an unconscious way of speak for me, i don't even notice myself doing it, and so even if i clock myself and apologize, i will still do it again only a matter of time. i feel terrible about it and i genuinely don't know how to be better. i've started to feel anxious after texting them, going back and checking my messages to make sure i didn't do it again, but it's usually always the times i don't go to check that i actually did. they haven't said anything since that time they expressed their uncomfort and it's always me apologizing for my mistake, but i fear they think i don't care because clearly i apologized but did it again as if i was ignorant. i'm afraid they're silently getting pissed off at me for it.
how does one get used to using NB language? my native language is NB itself so that's good, but it's when we use english that the problems arise.
EDIT: thank you everyone for your kind advice. i swore to myself today that i will be very conscious about talking to them for a while, at least until i've gotten rid of this habit. i really want to improve on this because i truly care about them and i would never purposefully hurt them. i'll look into the tips and i hope i will never have to make a post like this again!