Nas is in a strange situation where he is too rich for the hood but doesn’t really fit in with other rich (and presumably lighter-skinned) people. He talked about this in Black Republican, and it also forms somewhat of a theme on Life Is Good.

Nas is explaining the nature of people in the black community from a sociological perspective, specifically the idea that citizens are a “product of their environment.”

Essentially, this excerpt describes the notion that putting people in a different setting or scenario will have little to no effect on their basic instincts and behavior.

It leaves open the possibility that once you grow up in an environment, you may never be able to shed the influence of that environment. In that sense, people from the hood are products of their environment (or at least the environment of their developmental years).

He talks about it in this interview:
http://youtu.be/YuaJzK2i8as?t=36m10s

Nas' mother passed away in his arms of cancer in 2002, an event that sent him into a depression and carelessness that culminated in his failed 2002 Summer Jam attempt to hang Jay-Z in effigy and his famed rant shortly thereafter on rival station Power 105.1.

In the vh1 behind the music he said that what made him come back to music was that he could feel his mom inside of him and in the mother. He could move on:

that´s life. You keep living on.

http://youtu.be/K8VcczZtIeI?t=4m42s

Thats the feeling he is describing right here.

A round in the chamber. Common parlance to discharge a gun is to “cook one off” so here Nas plays on that verbiage.

Fortune favors the bold

The secret behnd his success of reappering on top is because he is never afraid of taking chances. For instance albums like Hip Hop Is Dead and Untitled are something many would call career suicide with all the shots and controversy stirring up.

Nas here realizes that things could be a lot worse, and takes inspiration from people who are overcoming real, life-changing difficulties. The line is also a pun – as the soldier has no legs, he just uses what he has left, his head.

We send him to the hospital, where he gets hooked up to IV fluids because they’ve fucked him up so bad…

The streets are figuratively calling to him, it’s inside his head a little bit but he knows he shouldn’t go back today. It says “today” because he’ll hear the streets calling to him again tomorrow.

He has stated that he doesn´t feel at home with the rich fancy people and feels more at home when he is visiting his old hood. That’s why he doesn´t want to visit too often, who can blame him? You can get shot and it´s not a good place for kids to grow up.