I am an eva music nerd. Refrain was an album of music "inspired by" Eva, mostly songs sung by Yoko Takahashi to my knowledge. I find it interesting how the song's obviously about childbirth, but is also about the latter half of EoE.

http://www.animelyrics.com/anime/eva/genwaku.htm

I watched the waters surface where the light swayed
as I floated in your sea

Listening carefully to the voice I hear,
I entrusted my body to the movements of the waves.

Ah...
The voice that calls me out of a light sleep
spreads out with a dizzy feeling,
becoming a ripple.

Only gentle times
pass by slowly,
without anything such as
loneliness or emptiness

As if being enveloped by the scent of that day
I want to keep sleeping right here, like this.

Ah...
Like a shell wandering between the waves,
I dream that I was
washed up on the shore.

I feel the sky,
coming closer and closer...
I can't tell
if it's real, or an illusion.

Ah...
The me you left behind lives on.
I'm just beginning to realize
I can't stay here.

The voice that calls me out of your sea
spreads out with a dizzy feeling,
becoming light.

the second-to-last phrase ("koko ni ite wa ikenai to
kidzuki hajimete") seems especially relevant compared to the EoE tagline at the beginning of the movie and on the poster--"dewa, anata wa naze koko ni iru no?" It's either that, or the "koko ni ite mo, ii no?" part. of course, Shinji also faces the realization that he can't remain in unbirth forever, in the end.