Full Idea
Anguish is distinguished from fear in that fear is fear of being in the world whereas anguish is anguish before myself.
Gist of Idea
Fear concerns the world, but 'anguish' comes from confronting my self
Source
Jean-Paul Sartre (Being and Nothingness [1943], p.65), quoted by Kevin Aho - Existentialism: an introduction 5 'Radical'
Book Reference
Aho,Kevin: 'Existentialism: an introduction' [Polity 2014], p.73
A Reaction
I'm guessing that the anguish comes from the horror of the infinite choices available to me. Once you've made major life choices with full commitment (such as marriage), does that mean that existentialism becomes irrelevant?