This paper presents a brief overview of current knowledge regarding the neuroscientific and biological background of anxiety and fear. The conceptualisation of the “two-system” framework is described in detail. In terms of terminology, the terms fear and anxiety are limited in this framework to mental states connected with consciously experiencing emotions as opposed to nonconscious autonomic nervous system reactions. The introduced terminology may have practical implications in psychotherapy as people seek help mainly because of subjective experiences of fear and anxiety and the effectiveness of mental health interventions is also evaluated on the basis of experiencing these mental states. The background of developing anxiety disorders is briefly described, emphasising the key role of sympathetic and parasympathetic systems. As nowadays anxiety disorders are prevalent among adolescents and adults, it is necessary to implement interventions preventing development of full-blown disorders in people suffering from excessive or sub-threshold anxiety levels. Acceptance and commitment therapy (ACT) is suggested as the evidence-based prevention model. ACT promotes building psychological flexibility, incorporates mindfulness techniques which enable alteration of the anoetic form of consciousness, and introduces breathing exercises that may stimulate the sympathetic system through the vagus nerve. Thus ACT model as a preventive tool has the implications to bridge the psychological and neuroscientific research and theory with practical usage.