Good on you for enlisting. The military is loaded with opportunity, and from my outside experience it gives people a chance who might otherwise be overlooked. I have two cousins, both younger than me, who had a hard time with school...now, they were not stupid, just lacked the focus to study and do well which really reduced their chances of getting into college on top of the fact that they neither one wanted to try for more school after having such a rough go of it already. They both joined the military (Marines and Army) and it really got them on track. Now, they're both responsible adults with families and jobs they enjoy. Without the military, they probably would have continued to be turds and I would have had to kick their asses.

My point being, don't let people discourage you or doubt your decision and make double-sure you laugh at them later when you're rolling around with your secure job in the field you trained for and they're stuck still looking for work. I wish you all the best and kick some ass!