This goes back all the way to the beginnings of Psychology. William James, who is considered the somewhat of godfather of Psychology, argued that all feelings are bodily feelings; ie. emotions are caused by bodily sensations. Your heart is not beating BECAUSE of anxiety, rather your beating heart IS anxiety. You don’t tremble because you’re afraid, you’re “afraid” (a complex emotion mediated by stories we have) because you tremble.

It’s a theory psychologists and philosophers still argue about.