They work throughout the day
Speaking, eating, concentration and emotions engage different groups.
Their activity is natural and a completely still face is not a sensible goal.
Tension may have different causes
Discomfort should not automatically be assigned to one muscle.
Persistent pain needs appropriate assessment.
Everyday muscle use is natural
Smiling, concentration and speech constantly involve facial muscles, so expression is not a fault to correct.
Treatment can offer space to notice fatigue rather than trying to remove expression.