Sometimes we feel something that just stick around our sense, and we just don't know what it is. It comes as anoying sensation, when it goes, we may feel glad - temporarely. But soon as it is returning, we don't know how it could give us a stressful moment.
So what is this feeling? Or the question should be, is this kind of feeling really exist? Or this feeling is something that sensed by our nature, or just something that came from our fear?