Do other people also get very acutely upset, sad, angry or scared over things that they don't have any control of and that they have known all their lives, for example the fact that we are all eventually gonna die?
I do, every once in a while, fairly regularly. From the reactions I get to it I gather that most people don't, and some have found this outright scary when I told them. A couple of people told me to get immediate help, but failed to convince me that I need help for this, immediate or otherwise (when you've been doing this all your life without noticeable ill effects it's kind of hard to believe in the problem's immediacy).
Those "moments" (or hours, usually) don't seem to be in any way correlated with stress, life situation, general health, general sadness, menstrual cycle, alcohol use, seasons, or anything at all.