You can no more choose your sex or gender than you can your arm length or gall bladder. Those were granted—or “assigned”-- to you…by the union of the two different, specific, complementary sexes that created you.
You can choose your words, but you can’t choose your gonads. When a buck deer sheds his horns, it doesn’t make him a doe. Moreover, though you can sew a horn on a horse’s snout, doing so doesn’t make it a rhinoceros. Or a unicorn.
Someone once said, “You Can’t Always Get What You Want.” There is such a thing as reality. Sorry, libs. Go have a good cry…and a warm cookie.
Or, better yet, grow a pair. (To those in the throes of gender dysphoria, I mean that figuratively).