This is beautifully written and i think there may be many different interpretations about this piece.

I try to stir you
gently
into my mug,
no sugar
no drugs
so when I sip my eyes
warm as my tongue
tastes nostalgia
and I am lucky
to be only
slightly
harmed.
^^
I like this opening you take something so simple and make it so elegant. The stirring of another so you can drink them and feel them within you is a pretty good image. You didn't add drugs or sugar which shows you took them all for what they were and only ended up slightly hurt, I love hat concept.

Images are buried
in my ribs then
wither
out of my mouth -
I see everything
I have apathy
yet I sense a barrier,
something blocking
the heart's ability
to speak
without words.
^^
Again lovely imagery of images being imprinter on somebodies rib not allowing them to escape and do you really want then to even if they do wither out your mouth? I love how you are trying to talk in this stanza but that something is stopping you, probably the fear of saying the wrong thing?

I need your liquid
comfort to tell me
that I am here.
Alive.
Human.
That I can feel,
sense pain in others
besides myself.
That these flashbacks
aren't forever cemented
in my brain,
that I will be able to
mourn for their
existence,
for what I learned
for I can no longer
walk with some of them.
^^
This is my favourite part because you are trying to come to terms with things from your past that are imprinted on your mind and want to let them go by speaking of them and feeling something real by sipping on someone's liquid, their comfort to you be wise in our times of need we all need comforting sometime.

I beg God to cry tonight...
Not selfishly, not to show
off to others but to
be able to feel the struggle
for sanity
again.
^^
Here I feel you are in a self pity mood not for yourself but for your sanity. You want to scream, shout, cry anything to let to?

Tears suggest that the pain
will soon fade away,
and I may someday breathe
courageously
without cinders and spirits
writing my shadow
for me.
^^
A wonderful ending. Tears do usually represent pain but they could represent something else, joy that you have your sanity again, you feel real again and can breathe without all this burden on your shoulders because you have let go of it.

Great write, Em