Emotional arousal= activation of the sympathetic nervous system.
Emotional de-arousal= activation of the parasympathetic nervous system.
One way to get intense, long-acting, and no-longer-useful-but-highly-activated emotions to go down quickly is to activate the parasympathetic nervous system through the use of the dive reflex. This is a reflex in mammals (picture seals diving in cold water) in which the heartbeat is slowed and major blood vessels are restricted. This means that less oxygen is needed in the bloodstream and thus the oxygen can be utilized for major organs. Bottom line: intense emotional arousal goes down.
Here are some suggestions:
1) Splash cold water on your face. This option may be more feasible if you are not at home and don’t have much time or privacy.
2) Cover an ice pack with a cloth or towel and press it against your face.
3) Fill a basin with ice and put your face in it; holding your breath for as long as you can.
PS. I assume there are some risks associated with cold cold water, take heed and use caution. I got these ideas from research studies available online related to the dive response.