Two lost souls

[xyroph]

One more bag
To put me right
Downward spiral
Dizzying flight

Meet me at the bottom
Where emptiness prevails
We'll plot our course 
And set our sails

Prevail seems like a strong word for emptiness to commit to. I do like the invitation to what sounds like "rock bottom" though. The darkness is very seductive indeed.

We'll make love gently
Or we could just fuck
We'll try to fly   
But find ourselves stuck  

Rhythm seems a little forced here. I'd like to know why they're stuck.
     
My heart beats slow
Your pulse grows weak
Our demons stirr
And begin to speak    
Whoa! This line, on its own, is a real heavy hitter, it definitely doesn't need the modification. 

if you really want to, maybe just make it bold in the same size as the rest of the type. The huge typeface is almost visually offensive.

This heat in our stomach
Poisons warm embrace
Death moves in
And shows its face

Sort of a vague ending. Maybe elaborate on these sensations: is the heat only in their stomachs? Is it spreading through their bodies? 

What is the poison doing to them? 

It's nice and brief, and the imagery is decent, but personally I think it could use some fleshing out.