I had a similar observation years ago while at a meditation retreat. I noticed that the order of causation was different than I thought when it came to emotions. I had believed that thoughts were causing emotions, and sometimes they do, but I also noticed that sometimes emotions were just arising randomly. Then within a split second my mind was assigning some reason for that emotion, a thought, and then the thought began to amplify the emotion. But if I stopped it at the moment of awareness of the emotion, and recognized the emotion as having no cause, it simply dissipated, passing on into the next emotion. Ever since then I've been very aware of when emotion is causing thought vs thought causing emotion, and have had a much easier time choosing my emotions at will.