How To Handle Children Who Are Sensitive And Nervous?

I was a very sensitive child...maybe even what one might call nervous. As I grew up as with most people, life changes all of that. It introduces you to a thicker skin and harder constitution, usually a good thing, a thing neccessary for life in the worl we live in. Lately, as in the last few months, I've noticed a difference in myself emotionally. I've become enitirely more sensitive then I've ever been in life. things that usually would have rolled off my back, hours later I fing myself still stewing over. Why am I sooooo sensitive lately?