There’s a storm inside of us,
I’ve heard many team guys speak of this.
A burning.
A river.
A drive.
An unrelenting desire to push your self harder and farther than anyone could think possible.
It pushes us into those cold dark corners,
Where the bad things live,
Where the bad things fight.
We wanted that fight at the highest volume.
A loud fight.
The loudest, coldest, darkest most unpleasant of the unpleasant fight
—  Marcus Luttrell
For those studying for the ASVAB

Here are some helpful sites: