1. A system configured to select a state of a user, comprising: at least one inward-facing head-mounted thermal camera (CAM) configured to take thermal measurements of at least three regions below the nostrils (TH S ); wherein TH S are indicative of shape of the exhale stream (SHAPE); and a computer configured to: generate feature values based on TH S , whereby the feature values are indicative of the SHAPE; and utilize a model to select the state of the user, from among potential states of the user, based on the feature values.