It's very clearly stated in the film: You make your own choices, and what you're always fighting is ego.
“People never improve unless they look to some standard or example higher or better than themselves.”
“If Iraq and Afghanistan have taught us anything in recent history, it is the unpredictability of war and that these things are easier to get into than to get out of, and, frankly, the facile way in which too many people talk about, 'Well, let's just go attack them.'”