Full Idea
Anxiety [angst] is the disturbing sense of uncanniness by which Dasein is overtaken (thrownness) when it discovers there is nothing other than its own freedom to sustain its projects (projection), and from which Dasein constantly takes flight (falling).
Gist of Idea
Anxiety is the uncanniness felt when constantly fleeing from asserting one's own freedom
Source
report of Martin Heidegger (Being and Time [1927]) by John D. Caputo - Heidegger p.227
Book Reference
'A Companion to Continental Philosophy', ed/tr. Critchley,S/Schroeder,W [Blackwell 1999], p.227
A Reaction
This seems to be Kierkegaard's idea, unamended. In my experience anxiety only comes when I am forced into making decisions by worldly situations. An 'existential crisis' is a sort of blankness appearing where a future life was supposed to be.