a common thing that people tag this post with goes something to the tune of:
"its fine if you dont get it perfect at first so long as youre trying :) but yeah its very obvious when people arent putting any effort in lol"
and like. i promise you do not have to play devil's advocate for cis people on this post yall. you don't have to offer leeway to the person being cruel to you. not only that, but people that misgender you ever will take a mile if you give them an inch.
cis people hear "its fine if you misgender me at first" and think of "at first" as five years or more. i'm not joking. they do this for a variety of reasons, but most significantly because cis people never stop thinking of you as "transitioning" even if you would consider yourself "transitioned".
cis people will also consider themselves adequately "trying" no matter what they actually do. this is due to a variety of reasons, but most significantly because they believe misgendering is what transphobes do, and they aren't a transphobe-- look, they haven't kicked you out of the house, have they?
there's a common line of thought, especially among white people, that there are two kinds of people-- racists and non-racists; transphobes and non-transphobes; misogynists and non-misogynists-- and they are the non-racist, non-transphobic, etc kind. that's not really how it works. how it actually works in real life is that anyone can do transphobic actions, no matter the ephemeral trasphobe/non-transphobe dichotomy they believe themselves to be in, and it's up to that person alone to correct their transphobic action. cis people often put themselves in the non-transphobe box, which they believe washes their hands of guilt-- they believe what they do cannot be transphobia, because they are not a transphobe.
cis people who believe this, and i promise you it's a lot of them, are in their minds perpetually "trying" to not misgender you, to make you comfortable, even if they've never once done so. so when you tell a cis person that misgenders you that it's okay to do it at first, and that it's okay as long as they're trying, they'll never ever stop misgendering you. because to them it's still "at first", and to them, they're always "trying", even if neither thing is remotely true. cede no ground to misgendering and deadnaming, outing and transphobia, even when it 'only' harms you emotionally and not physically. it's never worth it.