"We're women because we say we are - and that's really all there is to say about it."
It doesn't make any sense for someone else to tell you who you are. How could they know? Of course, if you were autistic or schizophrenic, that would be different...
Anyway, I remember reading an evocative description by a trans man of how testosterone made him feel like a sex crazed monster. Nobody can know for sure if they have the same experience, just like we don't know if the color blue is the same for us.
But it seemed to me that implied one of two things - either he was experiencing what cis males consider normal, and it was horrifying, in which case it was evidence against him being "really" male, or else he was not experiencing what being a cis male is like, in which case it was evidence that administering male hormones may not produce the effect of natural ones.