People say, "Well, you can be a tomboy just fine. You don't have to be a man to be yourself."
But they don't get it. I have a body identity, too. My breasts are a serious problem...
If someone said it would be "easier" to change my mind rather than my body, I'd tell them that it isn't. Testosterone is going to do most of the work with my body, simply by taking it. Not to mention that changing my mind would be very difficult, because I have the legitimate symptoms of a legitimate disorder. Being more feminine would not make my body dysphoria go away, nor would it change the core identity of who I feel I am. Gender is a package deal; it acknowledges body identity, mental identity, social identity... a lot if things. It's hard to change all of those things to match your birth sex if they don't already. This isn't something I can change my mind about, as it is considered a true illness by the medical community. In other words, it can't really be "undone." Anyone who thinks we all haven't tried that at some point is pretty shallow minded. I'm sure a lot of transgendered people wanted to just be normal, cisfolk.
People ask me how I know I'm a guy. So I ask them how they know what they are. They just know and it just happens to match with their body. They don't think about it much because it causes them no trouble. Most cisfolk I know tend to mash gender and sex into one concept, so they can't even begin to understand.