My Sadie is the bomb proof dog, very little phases her.
Ginny is definitely more sensitive, I always have to watch her for her reactions but in general, I'd say she's a pretty normal, sensitive sheltie.
Toby is on the opposite side of the spectrum from Sadie, my bomb proof girl. I learned from dealing with him that sometimes positive training, patience and understanding can only get you so far.
"....with limited ability to handle stress. Their behavior can be rigid, maladaptive, inflexible, or even downright fragile. These dogs can experience poor quality of life at times due to specific stressors or stimuli (for example, thunderstorms). Or the dog may have a generalized inability to adapt that affects the dog throughout his life in many or even all situations."
Yep, that's Toby, who has little to no ability to cope with certain situations and triggers. He is VERY fragile, it takes VERY little to traumatize him.
Even though he's come a LONG way from where he was that first year we had him, we've come to accept that Toby will never be 'normal' like my two girls.
Everyday life with Toby is still a challenge. I've spend so much time watching for stress signals from him (at home and when we're on a walk and listening and looking for things that might set him off that I've gotten in the habit of doing it even when I'm away from him.
A lot of thought, time and effort is put into attempting to pre-determine what Toby can handle, keeping him out of situations that I know he cannot(or limiting his exposure to these situations) and making life at home as comfortable for him as possible.
I found this article really great too. I'm not sure if I missed reading it when I was dealing with Toby a few years ago or if she posted her article after I stopped looking, but I wish I'd seen it when I was struggling with him over whether or not to medicate him. It would have been really helpful.
http://suzanneclothier.com/the-articles/3-ps-does-your-dog-need-medication