I have Asperger's, which is in most ways very similar to high functioning autism. On the surface you wouldn't be able to tell I have autism, because I'm very fortunate in that one of my only hindrances are difficulties socializing. Unlike a lot of others who have forms of autism I can actually read and interpret the meanings and intentions behind other people's words, action, and expressions fairly well, but I often over analyze them, which makes me really anxious, and a lot of times I worry that people don't like me or are somehow upset with me, so I'm always pretty nervous when interacting with other people (which I try to avoid as much as possible) and trying to be as nice as I can to them so that I don't somehow upset them or make them dislike me. This is also tied with hyperempathy, which I saw someone else talk about in their comment below, but to quickly summarize it, it basically means that I feel most emotions at a greatly magnified level, and I empathize with the emotions of others in the same way. As I'm sure you can make the connection, this means that when I interpret others as disliking me or being upset with me, it gets significantly magnified beyond how most people would feel in that situation.

Like a lot of other autistic people, I have very pointed and deep interests. I have a few, but my biggest is music, specifically guitar. I spend basically all day either listening to guitar music, my favorite stuff being complex and busy arrangements like 70's style progressive rock (bands like Rush, Jethro Tull, Yes, and King Crimson), playing guitar, or watching informative videos/reading articles on guitar gear, playing techniques, styles, and things like that. I have a hypersensitivity to a lot of stimuli, especially sounds, which actually helps me out here, because I didn't actually start playing guitar until my first year of high school, but because I can hear the nuances in people's playing styles, all I really had to do was watch and listen to how people played to learn what they were playing. That really helped me progress much faster than it most people, because I've only been playing for about 6 years now, but I can play a lot of more complex and difficult things that most people who have been playing this long can't. My dream is actually to be in a progressive rock power trio band that tours around the world.

A lot of people talk about autism as feeling like you're isolated from everyone else, and I'd say that that's pretty true. You don't really feel like you fit in very well, and you wish that other people could see or hear or taste things the way you do, because trying to explain to them what it's like to have autism without them experiencing it for themselves is hard to express in words. A lot of people say it feels like being a fish out of water, but to me it's always felt more like being a fish in your own bowl, or maybe more accurately a fresh water fish in the ocean water with the salt water fish.