Boo! Daniela Neu on beyng's disclosure by selfconcealing in fright.
In section 122 of the Contributions, Heidegger thinks the leap by recalling the existentials of Dasein in Being and Time which are Dasein's opening projection of possibilities of being and its thrownness into possibilities of being. The leap into the truth of beyng is thought, in section 122 as the “enactment of the projection of the truth of beyng in the sense of the moving into the open in such a way that the thrower of the projection experiences himself as thrown, i.e. en-owned by beyng”. The emphasis lies here on the “throwness” of the projector which is experienced in the enactment of the opening projection of the truth of beyng. This thrownness is now thought in terms of thinking's (Dasein's) enowning. If thinking leaps into, if it gives itself over to the original occurrence of the truth of beyng - which occurs as withdrawal - then, in this withdrawal it experiences as well its enowning through beyng as withdrawal. Thinking experiences its coming to be out of beyng's withdrawal.
Yet this enowning of beyng occurs 'only in so far as thinking holds itself in the open, if it is “in-sisting” [inständig] in the truth of beyng, which occurs in what Heidegger calls “retention” [Verhaltenheit]. Retention is the name Heidegger gives to the ground-attunement in which the truth of beyng originally discloses in the transition from the first to the other beginning of western history. It oscillates in a variety of moods. Besides the “retention”, Heidegger names, in section 5 of the Contributions, “fright” [Erschrecken] and “awe” [Scheu] (in other sections, Heidegger speaks also of the “pleasure of overcoming” [Lust der Übersteigung], of “presentment” [Ahnen] and horror [Entsetzen], yet in the more líteral sense of being unsettled). Fright, says Heidegger in section 5, is “being-driven back” [Zurückfahren] from the familíar behavior “into the openness of the nıshing forth of the self-concealing” [in die Offenheit des Andrangs des Sichverbergenden]. In fright, beyng discloses itself as selfconcealment. We can think this attunement in relation to the anxiety of which Heidegger speaks in Being and Time. In anxiety, Dasein's familiar relation to beings withdraws and it is faced with its utmost possibility of being; the possibility of not being at all. This possibility of not being at all which constitutes, in Being and Time, the finite horizon out of which Dasein occurs in its temporality, is rethought, in the Contributions, as beyng's withdrawal in which Dasein is enowned. Now, in order to hold open beyng in its withdrawal, thinking needs to be attuned also by “retention”, because in retention, there is the moment of the turning toward the withdrawal [die Sukehr zum zögernden Sichversagen]. Both, in thinking's being driven back from beyng's withdrawal and in being turned to it, beyng is held open in its withdrawal, its selfconcealment held in “hesitation” [Zögerung]. Thus, the time-space of beyng's hesitating withdrawal expands when thinking holds itself in the re-tension. This moment of holding oneself in the hesitating withdrawal is further intensified by the “awe” [Seheu] which involves a “keeping silent” [Verschweigung] in which beyng is given free to occur as enowning [Wesenlassen des Seyns als Ereignis].
From "Overcoming the Ontological Difference in Heidegger's Contributions to Philosophy