People can survive in all sorts of ****ed-up conditions: no arms and legs, faces rotting off, giant tumors growing out of their heads. Just look at developing nations, the stuff people manage to survive for decades with.
A transexual person has survived in a grotesquely malformed body for decades: since birth, to be precise (which is to their credit, and points to their fundamental psychological fitness and health).
But every day has undoubtedly been a torture. One does not "get used to" hideous deformities.
One might live with them, but I'm sure one never loses hope that somehow, someday, one will be "fixed", freed from said deformity.
One gets up each day in a deformed body; one drags oneself through the days, because there is no choice, no immediate solution.
No one could thrive under such circumstances; their loathing of their bodies and their discomfort in them no doubt colors every minute of their lives.
Sex reassignment surgery in such cases is as humane as separating conjoined twins, as reasonable as removing a giant esophageal tumor that is slowly strangling off the person's breath.