For me, it was that I needed to do something with my life.  After I high school, I went to a community college for one semester.  I skipped classes for 2 months, but still had an A average ... I realized I wasn't ready for college so I quit.  I figured that I needed to do something and I like airplanes, so I decided to join the Air National Guard.  While I was talking to the recruiter, 2 buddies of mine came home from Marine boot camp, and I was blown away by the difference in made in  them, so I went in the Marine Reserves instead. 
  
When I went back to college, it gave me more discipline to work harder.  I was more disciplined and more mature, especially after I came back from Desert Storm.