Full Idea
Because Dasein is lost in the 'they', it must first find itself. It must be 'shown' to itself in its possible authenticity. In terms of its possibility, Dasein is already a potentiality-for-Being-its-self, but it needs to have this potentiality attested.
Gist of Idea
Dasein has the potential to be itself, but must be shown this in the midst of ordinariness
Source
Martin Heidegger (Being and Time [1927], II.2.54)
Book Reference
Heidegger,Martin: 'Being and Time' [Blackwell 1962], p.313
A Reaction
I wish there was some criterion for knowing when you are being yourself and when you are not.