Sentence:  LRRP planned to become “career” Army, i.e., a <WSD>lifer</WSD>, you kept that quiet. Basic LRRP theology said the Army sucked and that philosophy kept one from going crazy because, at the bottom, nothing about the war seemed to make sense anyway. The LRRP's considered a <WSD>lifer</WSD> a loser. Being a <WSD>lifer</WSD> implied one had no  other options available. Every LRRP had his own stories about back home: about family, friends, lovers, opportunities, dreams and a future. These were mostly fantasy, but ... 
Meaning of the word marked with <WSD> tags:  A person with a singular career path, especially in the military.