I think I wasn't shy when I was a little kid, but I became shy.
I have a good amount of friends, but with anyone else besides them I do feel anxious and do not relax around them even after a long time. I usually hardly speak in social situations (that aren't made up of mostly friends of mine) because I'm aware of every word and how each one might come out wrong.
I think some ASD people aren't anxious because they might not be aware of how they're coming across in social situations, or for some reason they don't care, but many do.
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"You gotta keep making decisions, even if they're wrong decisions, you know. If you don't make decisions, you're stuffed."
- Joe Simpson