Full Idea
The formal existential totality of Dasein's ontological structural whole is: the Being of Dasein means ahead-of-itself-Being-already-in-(the-world) as Being-alongside (entities encountered within-the-world).
Gist of Idea
Dasein is ahead of itself in the world, and alongside encountered entities
Source
Martin Heidegger (Being and Time [1927], I.6 41)
Book Reference
Heidegger,Martin: 'Being and Time' [Blackwell 1962], p.237
A Reaction
If you find that thought really illuminating, you are probably on the wrong website. However, the thought that we exist 'ahead of ourselves' might be a fruitful line for existentialists to explore.