I believe a big part of it is one of the stages of growing up. I can only tell you from personal experiences though. I was once more of a sensitive gal as well. Tough experiences made me a stronger person. There are a lot of situations that happen to me personally or happen around me where the normal response is to get emotional and cry but I usually don't. It doesn't mean that you don't care. It doesn't mean that you are heartless. It means you've learned to look at things in a different way and you've learned to cope differently. Although I don't shed tears often anymore, I find myself laying awake at night drilling my brain with thoughts about certain situations. Instead, I experience anxiety. I've found a lot of people grow old and regain certain sensitive expressions. Another stage of life and neither of us will understand it until we get there. To find you posting about your worries in fact shows that you do care. You are a strong person. Don't let the common belief make you think otherwise, friend.