Interpol has said that the majority of their music is up to interpretation and that there really is not a set of specific meaning behind their songs, including 'Obstacle 1'. SongMeanings.com has a variety of opinions due to Paul Banks writing obscure lyrics, but that's the beauty of Interpol. It's up to us to listeners to give meaning to the individual song. Of course, there are songs that do have more specific meanings (like 'Rest My Chemistry' and 'No I' in "Threesome").

In the interview referenced above Paul touches on that very subject. He says, "I don't really feel like being too obvious so I think that the fact that people can have differing opinions is also fine because life is sort of up for interpretation." This is what he carries on into writing for Interpol. 

zen-take: So who can cut through the ambiguities? What you hear & see depends on what you want to hear & see. Depends on how receptive you are to what kind of imagery. Free-form it. 

Is the object of affections deceased? Does this lyric have to do solely with remembrance of things past? The Or is only the relationship dead? Or dying or troubled?

The protagonist is concerned that poverty & age enter into the equation. "God please don't let me look poor...or old...!"  But such disappointing realities might be overcome. Or is that merely wish-fulfillment illusion? 

Obstacle 1

I wish i could eat the salt off your last faded lips
We can cap the old times make playing only logical harm
We can top the old lines clay-making that nothing else will change.
But she can read, she can read, she can read, she can read, she's bad
Oh, she's bad

It's different now that I'm poor and aging, I'll never see this face again
You go stabbing yourself in the neck
It's different now that I'm poor and aging, and I'll never see this place again
And you go stabbing yourself in the neck

We can find new ways of living make playing only logical harm
And we can top the old times, clay-making that nothing else will change.
But she can read, she can read, she can read, she can read, she's bad
Oh, she's bad

It's different now that I'm poor and aging, I'll never see this face again
You go stabbing yourself in the neck
It's different now that I'm poor and aging, and I'll never see this place again
And you go stabbing yourself in the neck

[Chorus]

It's in the way that she posed,
It's in the things that she puts in my head
Her stories are boring and stuff.
She's always calling my bluff.
She puts the weights into my little heart,
And she gets in my room and she takes it apart.
She puts the weights into my little heart,
I said she puts the weights into my little heart.

She packs it away [6x]

It's in the way that she walks
Her heaven is never enough
She puts the weights in my heart
She puts, oh she puts the weights into my little heart.

--song written by Interpol