Ohh wow, yes, I can relate to this. My son breaks down a lot, sometimes its over nothing and then other times its over something really deep.
The other day I looked over at him and I could see tears welling up, so I asked him what was wrong and he burst into tears saying "I don't want you to die". I said "I'm not going to die, yet" and he said "but you will eventually" (I'm getting teary just thinking about it). Then on the other hand, this morning he was crying because his teddy dropped on the floor outside and may have gotten dirty. Sometimes I feel like saying "are you kidding me?".
I tiptoe around him more than I should, but I know that little things can set him off and his feelings get hurt really easily. He can be emotionally draining, in fact all my kids can, sometimes I need a break. I totally get where you are coming from.