From moving around a lot in my childhood and negative brushes with others I have developed a hard shell. I walk around often with what I call a "perpetual scowl," I'm quiet, hard to get to know, and very private. All of these things are a defense mechanism surrounding what is in actuality a sensitive person. At some point, though the shell starts to become the person and it has made me colder, more sarcastic, and slightly apathetic (though never to the extreme of any of these). After one move I decided that I could be a island and didn't need to form new friendships--friends were difficult to develop and harder to keep. I lived this way for over a month (always alone, even rebuffing some offers of friendship) before I realized that while I could be alone it was better to have friends (and the inherent drama there of).
Lately though, my shell is breaking down both outwardly and inwardly. I can see myself becoming softer, boosted by good friends and positive experiences. It is warming to be around people who are caring and kind, but frightening to realize that part of my "safety" is disappearing. (When you can't feel anything no one can hurt you.)
I'm noticing how hurt turns to anger for some and sympathy for others. For me, I err on the latter. I think that people who have really been hurt, cut very deeply by others know the most empathy and are sympathetic. When you have been the odd man out, the victim, felt under constant barrage, it's a feeling you wouldn't wish on anyone else or contribute to. Instead of lashing out, you quietly defend or empathize.