Tank, there's actually a movie where this little boy wants to be a girl, and has longish hair so that he actually looks a bit like a girl. His parents forcibly cut it at one point, and he's pretty traumatized. It's called "La Vie En Rose." Of course, that's just fiction.
I've also read stories about girls with braids and somebody cuts off part (or all) of a braid, forcing them to cut the rest of their hair to match. Or Anne of Green Gables, who tries to dye her red hair black, ends up with green, and has to have *very* close-cropped hair until the green grows out. But, again, most of the stories I know are fiction, so that doesn't give you the *real* feeling.
What if you imagined something that were roughly the equivalent? Something done to yourself that is either irrevocable, or at least long-lasting, and changes the way you look or mars the way you look for a long time. Like somebody forcibly giving you a tattoo, or cutting your face and you fear that it will scar. Maybe those are slightly more permanent than a haircut (although tattoos can theoretically be removed and scars may be improved with cosmetic surgery), but it's something that would take considerable time or money to fix, and meanwhile would leave you looking different.
