Informal Theory: Question Regarding Medical Affect

Medical affect is divided into long term mood and momentary emotion.  I don't quite see the mood swing. I understand that to be up and/or down. I'm staking a hunch that pendulum motion based theory occupies a lot of the area research. Though if there are two subcategories that overlap over time or maybe on two distinct time dimensions then does pendulum theory really suffice? Or more like can another dynamic motion theory be used in operation? Pendulum theory can approach wave complexity with use of Foucault pendulum like used as a mirror interferometer in telescopes. Is that though base enough when approaching complex multioscillatory systemic fields of the human body? Are we conceptually too given over to grand symmetries?