I have been watching "Six" and comparing it to what little I know, just being a friend who is often out of touch for years. It seems to hit on a lot of issues that conceivably arise.
Although my work on drill sites was nothing like their deployments it shared the element of I have to go when I have to go, I have to take the things I will need, and I'll be home when we're done (whenever that is).
That alone can put a lot of stress on a relationship (it killed one marriage, and that is getting off light in the business), and though once in a rare while things got a little dicey, that was the rare exception where I worked on drilling rigs, rather than the minute to minute danger those guys go through in training--not to mention on an op.
There are few people in life who summarily have my respect, and have to earn their way out of it. Those guys and their wives have mine, and those folks in that business I have had the privilege to know have never lost it.
Even in peacetime, there can be inordinate stress. I was lucky to be a SHORAD (Short Range Air Defense) officer - Chaparral/Vulcan. Women were barred from serving in these units. During '78, the Secretary of the Army ok'ed allowing women into rear echelon units, such as Nike-Hercules. This was done, of course, without upgrading remote facilities for the influx of female soldiers.
Male E-5s and E-6s had to move back into the barracks, while females no matter the grade were allowed to live off-site. It was awful for all concerned, let alone mission readiness.
About 1/3 of my ROTC class made it through Ranger School, the farthest I got was Airborne School...I was never a runner, and was not one who could go for weeks on very little sleep.
When it comes to Rangers, SEALs, etc., my definition for them is simple: these are Olympic athletes,
with weapons.