My old friends try their best. They get it right about 99% of the time (closer to the full 100% now though). That includes pronouns.
New people were interesting. I was using a shortened male version of my birth name when I started to study (new city, knew nobody, was already FT, didn't feel like explaining the difference in my "known as" name to my legal name). I changed it (legally) to something completely different about 2 months later, and after an initial week or two of occasional slipups they adapted just fine. Sure, nobody knew the real reason why - but they didn't need to.
My family... yeah. They haven't changed at all. I'm giving them more time. They might change (but probably not) after I'm on T and my appearance changes. They know I've legally changed it anyway, so at least I get my mail

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I think it's harder for people that know you in a previous presentation to adapt. They look at you and still see exactly the same person as they always have. Of course they're going to slip up - especially if they've known you for a long time.
Slip ups aren't always a lack of support, and sometimes it can be hard for us to chill out, step back, and see that they may be accepting and trying in other ways (slip ups not being an outright refusal, of course).
It's not always about people not "getting" you, but in order for people to "get" you then you have to give them the correct data to "get" in the first place! You can't expect them to understand how important it is to you, without telling them - they're not mindreaders.
This doesn't mean to out yourself (though you'll have to eventually anyway if you plan on full transition, and it is the easiest way to tell the truth and get it over with), but you do need to tell them just how important it is.
Expect people to take your name a little more seriously once you've been using it for a while, and it's legally changed. Until then some people might still assume you are "trying it out" or "considering" changing it.