Moving muscles and feeling emotions are linked.
When asked to contract smiling muscles it is hard to feel angry. If contracting frown muscles hard to feel happy.
When watching someone's emotion the same part of the brain activates as if it is happening to you.
You may need to consider ways you're interacting with people and the emotions you're expressing.
Watch out for unintended facial expressions.
Showing a video of someone being happy will change the perception of the viewer and influence their next action.