I think when you've been diagnosed late in life, as I have, some of the biggest frustrations are trying to explain to someone or someones we are close to that we are not the person they always thought we were. We've hidden things so well and have had so many years that we've learned how to get by that other's are unable to see any problem because we've done it.
They've always seen our guirkiness "but everyone has some quirkiness". I've heard - "But you are empathetic" (I'm compassionate, don't think I'm really empathetic). "You're not THAT smart" (ok, thank you.) "You're not obsessed with any one thing" (that you know of).
I think the person that most disappoints me is my oldest sister because I've always tried to talk to her about things I felt and how I felt different and stuff. In the past I have told her how I hated at work feeling like I was guilty of something and trying to not be caught but didn't know what I was afraid of being caught at. (once diagnosed realized it was fear of being found out who I really was because I didn't know who I was or why I didn't belong on this earth). I've told her about feeling like I was in a box that kept me from doing things and how I would freeze or not be able to get out of my car when I was traveling, or how anxious I was around ANYone and didn't like going to other people's houses, eating the same foods, watching the same shows, needing to do the same things. Everything I've told her in the past was finally explained through my diagnosis and she still would not accept it. I used to bore her to tears - I'd follow her around the house telling something while she probably was trying to get away. Oh, she also questioned that I did have friends. Neighbor and school mate, Val - I never liked her and she never liked me but we were forced to spend time together. High school friend, Cheri - we became friends because I didn't want her to beat me up. Later in high school I did have a friend that I spent more time there than at home - she was an adult. Cousins are forced friends. Lived in Alaska, Wyoming, Utah, Texas, Montana, Michigan, and other places and never even met a neighbor. Lived in Kernersville for 20 years and most people didn't like me, but I did have 1 friend. (We lost touch though). Moved here and have no idea how to make a friend of people my age and had talked to her about how frustrating it was moving somewhere and not being able to make a friend. And now when I tell her anything about myself she automatically goes to - "Oh everyone does that to a certain extent".
Now she humors me basically, but I HAVE found that if she calls and I'm wanting to get off the phone but don't know how to end a call, I can start talking about the autism and she'll soon say she needs to go.

I like having that tool to get off the phone, but it's still frustrating that the one person who I thought knew me the best will not accept my diagnosis as an explanation for all the things I've ever told her.
Funny, my kids had no problem believing me - but they lived with me. lol
What have others diagnosed later in life experienced in reactions of others?