The belief that being the opposite sex would be far more fulfilling is (ironically) further evidence that a complete transition to maleness or femaleness is impossible. For how can you identify as a man without ever having experienced the limitations and humiliations of being male? Part of being a man is to know, at first hand, how unfulfilling, distressing and embarrassing it is, and to feel solidarity with others who have had such experiences. To be a woman is, I assume, similarly unsatisfying, and women feel a bond of fellowship with others who menstruate, give birth, are patronised by men, and so on.
We cannot completely transcend our bodily limitations. This is a truth of the human condition, not just in terms of gender. While it is common to envy the perceived advantages of other types of humans (richer, taller, slimmer, whiter, more talented), most of us learn to live with who we are. It is a sign of maturity, but, then, we have no other option.
Feeling so completely envious of the other gender as to want to become it, is to ignore the fundamental difficulty we all share of being a small, individually powerless, fallible, ignorable human being who is all alone in the world, plagued by degrading physiological urges and afflictions, and fated to die soon. This afflicts us all, even the beautiful people. Failing to recognise this in other people means you are not seeing them as fully human in the same way as you are, even as you envy them. Desiring to be what you conceive of as not fully human is a desire for self-destruction: existential lobotomy or suicide.
The belief that it is your inalienable right to choose your gender, to destroy yourself, is a neo-con consumerist myth: the fundamental rights of humankind have degenerated into the shrill demand to be allowed to buy whatever you fancy.