It could be that this unhappiness is not your own. You might just be sensing someone else's unhappiness. It might be A, B, or C, or someone else in your sphere. We are all intuitive beings and often we pick up the thoughts and feelings of those around us, it's very common and happens every day. However, sometimes it's tricky to know which thoughts are our own and which ones came through in the "radio waves" from other people. I know it sounds weird, but think about it: haven't you ever walked into a room full of people and sensed a certain mood? Feelings can be contagious!