there are veteran groups explicitly set up to help people quit. Look at some of the early episodes of "Eyes Left" they used to mention them a lot.

I'm sorry, I was a bit rash in my earlier post. Unfortunately I can only speak confidently on shit that pertains to the army reserve and not the army national guard. I'm assuming the policies are very similar, but I also realize that each state can also establish their own policies as far as how harshly to punish guardsmen who fail to report for duty, whether it's on a typical drill weekend, or if it's for an activation under title 10/32 orders.

Honestly, in my time as a commander for my reserve unit, anytime I had a soldier fail to report for duty, I'd just excuse them or whatever. The most I could do was try to process them for separation under a general, other than honorable discharge.

For the guard, it's an entirely different animal - similar, but different. There's way too many different variables, so I'll just hold off on conjecture and say that the resources others have provided are good avenues to go with.