In Heidegger's philosophy it's found a diagnostic of our problematic time, he called it das Gestell, namely, the essence of the technical era. This essence is a dangerous destination of Being, because it involves forgetting our mortal condition. Against this problematic time, Heidegger has a proposal: serenity. Through this attitude is achieved to remember our forgotten mortality. This implies to recover our position in another destination of Being: das Geviert, namely, the fourfold. In this destination we need to let us be what we essentially are, and in this way dwell as mortals on earth.