It's true that someone sensitive can put up an adaptively protective front, even if it's not being consciously done, as a form of shield for their increased sensitivities. A person tends to numb through jading themselves to their experiences, gaining a tolerance overtime through the experiences themselves. Someone sensitive will be hit harder by strife, so it can be safe to say that they might jade that much harder, work that much harder than otherwise if they don't end up just perpetuating their sensitivity through avoidance.
Sensitivity in that way offers less room for a gray area, from what I've seen. Compensating for the strife of life is a balancing act of sorts, and those with mental afflictions tend to work that much harder to get over their problems in favor of blending in and not making a scene. "I don't care" tends to be the protective mantra of such types from quite the opposite being true.
Personally I'd say I am quite sensitive, but from living life I've been conditioned that much more not to be. Every failure because of it was a reminder of why I couldn't let myself be that way, and by choosing not to ignore it an increased tolerance against it formed. The shield I carry can no longer be lowered by choice.
"She said the only thing that stands out to her about when I was very young. Was that I didn't cry allot and that I didn't need to be held or pampered as much as my brother did."
My folks said I was also rather easy as a baby and as kid, but that didn't negate the existing sensitivity. I also had sleep difficulty back then too, so that might have been a factor, but most of my sensitivities were an internal struggle as opposed to an outwardly obvious thing. If anything, said sensitivity was likely internalized from being too afraid to let others see it.