Any negative feeling is ego, and ego sits on a fear
Fear is difficult to find by looking for it. The material says so directly — fears are hard to detect precisely because ego and belief are so good at covering them up. Ask yourself what you are afraid of and you will mostly get a shrug.
Campbell's way round this is the most practically useful thing in his whole corpus. You do not hunt for the fear. You watch for its receipt. If you feel anxiety, if you feel hurt, if you feel anger, if you feel insignificant — any negative feeling at all — that is ego. And the ego is there because of a fear.
So the negative feeling is not the problem to be managed. It is the pointer. His question for following it is plain and unsubtle: what causes me to feel angry, to be upset? Why am I upset? Keep asking and you will find a fear underneath, and it will be about you.
He gives this as a standing daily instruction rather than an exercise: every time you feel upset, every time you feel annoyed, every time you are unhappy about something, go and find the fear feeding it, and try to let it go.
Today you are only doing the first half. Find one. Do not try to resolve it.
Campbell, Buddha at the Gas Pump interview(opens in a new tab)