When I first was introduced to the prospect that people are not always cisgender, I was absolutely confused more than anything else. Trans people around me would describe how they experienced gender, and I would mull it over for a long time--how could they be trans if they described feeling exactly like I did, and I wasn't trans? Isn't that just how everybody felt?
I was talking about this with my first queer therapist at the time, and she invited me to consider: how did I know what gender I was?
All of a sudden, things changed for me. Trans folks were no longer other people living separate lives, completely distinct from mine--I was a trans person myself!
At first, this was terrifying, to be honest. I had been given a whole road map to follow for my life as a person assigned female at birth, and suddenly I was realizing that a lot of those things weren't guarantees--in fact, they were actually entirely optional.
This kept happening for me as I got more involved in my local trans community. All of the rules in my life that I had clung to for so long started seeming less absolute, less restrictive, and more like something I could CHOOSE to take or leave based on what I wanted to give structure in my life.