Same for me, watching a movie (one example that pops to mind right away, Sisterhood of the Traveling Pants) or girls in real life, seeing them with friends, how happy they seem, getting along doing the things they enjoy together and while I smile, at the same time inside I'm upset that I never got those kind of experiences. What's stopping me now, right? I can't go back to those youthful times as a girl, but can create similar experiences now as a woman. But so many years of solitude make it far more challenging than typing up these words.
Two social examples that still hit me occasionally, that why couldn't I've been one of them...
Back when I was really young, elementary school still, there were times (only a few, since I gave up the idea of trying) that I had tried to wiggle my way into playing with the girls jumping roping or playing hopscotch together, but being a boy I was told I couldn't play with them, go away! I wandered off, by myself, head low, walking around with no one to talk to nor play with. Only times that was fine was when it was something that all the kids, girl and boy would be playing as a whole, but I was still a boy. I was excluded from playing with the girls only, and the boys when all together were too rowdy and rough, I didn't fit in either way.
There was one time also during those early years of my life when we'd (my father, brother and I) would go up to Massachusetts (we lived in Virginia) every Christmas for the big family get together, but at a time when all us cousins were getting older (I was the oldest, going into my teens by then), so not playing together as we had years before (not my choice, they all thought the games we used to play were too childish), things started becoming more adult-like (I wasn't ready to grow up), and I remember several of my girl cousins sitting on grandma's porch talking, girl stuff of coarse, and I sat down to listen, because for some reason it just interested me, they got up and walked away to continue without a boy eavesdropping. I felt alone, that was not a good year there for me as most of the time I just wandered around outside by myself.