I'm Thin-Skinned

 "Thin skin" is a metaphor meaning sensitivity to critical comments/insults, etc.

I'd argue that with age I've become less sensitive to criticism than I used to be, although I'm far from insensitive to criticism.  (I always thought I was successful in not showing it, but now I doubt that.)

But the reality is my aged skin is much more susceptible to cuts and tears than it used to be. In my gardening I often become aware that I'm bleeding, bleeding without ever sensing what happened to break the skin.