The idea that being trans* is a choice, a conscious decision, is a powerful and very harmful myth. I already alluded to this issue in another article, but without going into the details.
First, I’d like to clarify something. By “being trans*”, I mean that your gender identity is different from your birth assigned gender. Being trans* is an objective category in that it does not require self-identification into this category. The same applies to being cisgender: if your birth assigned gender and gender identity match, you’re cis, and that’s it. As an objective category, being trans* is the direct consequence of gender identity. For example, I identify as a woman, but since my identification as a woman is different from my birth assigned gender, I am also trans*. To establish a sort of parallel, it is like being White or a person of colour: whether it is part of your subjective sense of identity or not, you are in that category and have different experiences from people in the other. Of course, different issues are involved, but I think it helps to understand. To conclude on this, being in either objective category does not mean that subjective identification will follow: for example, some trans people don’t identify as trans, and most cis people do not know the word exists.
Another little distinction I would like to establish is between gender identity and gender identification. Maybe there are better words, but I don’t know them. By gender identity, I mean the underlying impression of one’s gender. By gender identification, I mean the process of expressing and defining gender identity. Gender identity and gender identification may or may not match.
In fact, the first choice trans* people do is their gender identification: am I agender? genderqueer? female? male? transgender? bigender? pangender? transsexual? queer? a trans woman? a trans man? non binary? something else? People with similar experiences of gender may use entirely different words to describe themselves, and even the same person with the same underlying gender identity may use different words if they come to understand their own experience in a different light. There is also a choice to be made when using these words in context: to give a quick example, I strongly identify as a woman and less so as a trans — I am more a woman than a trans woman –, but when I’m within the trans* community or doing trans* activism, my identity as trans will be stronger and better asserted.
But the most important choice, which encompass the latter, is transition, i.e. asserting a gender different from that assigned at birth. It is a really difficult choice involving several other choices. In addition to wanting to transition at all, one also has to decide what this transition implies: Social transition? Legal? Physical? And what in each case? What name? What pronoun? What asserted gender identification? What gender expression? Hormones? Legal or black market? Surgeries? Which ones? And so on.
However, all these choices are built upon a stable bedrock: gender identity, following the meaning I gave above (“the underlying impression of one’s gender”). The choices I mentioned do not change gender identity, although they may help to understand it. In my opinion, you can’t really know what you gender identity is in the abstract, but you can know your feelings with regards to your gender by introspection and by trying new things to see how you feel with them.
What happens is that the more something matches gender identity, the more happiness and well-being will result; and if it does not match gender identity, the result will be gender dysphoria. A FAAB with a female gender identity will be fine from the start in many ways. A FAAB with a non-female identity, on the contrary, may use a variety of tactics to deal with it: they may do nothing at all, but they may also proceed to a transition — for example, by asking for neutral pronouns, by presenting a masculine gender expression, yet keeping their original name, or by taking hormones and requesting surgeries, presenting as androgynous and using a clearly masculine name. Some of these decisions will work, and some will not, but the closer each decision will be to their gender identity, the better one will feel with regards to gender. (This does not mean that transition is necessarily the right decision for the only reason that it will create a better match with gender identity. Feeling great in one’s gender but being abandoned by all one’s family and friends and losing one’s job is not necessarily a change for the better.)
As such, it is misleading to frame transgenderism as a choice. Transition may be a choice, but dysphoria is not. If there is a choice, it is a choice between misery and transition (which may also be miserable in its own way). Gender identity itself is not a choice. The only decision available is how you deal with it in order to lead a satisfactory life.