How would you feel if I lie to my girlfriend about my time in the military?
Are you for real? Why would you lie to her about your time in the military?
I don't want her to worry about the gory details of being in the army. She's more sensible than me. I would have more fun, whereas she would have a more troubled time.
I know you're trying to help, but it's wrong to lie to your girlfriend about anything. You can keep the details private and say you don't want to talk about it if you're afraid it will hurt her, or you can warn her and ask if she's sure she wants to hear it before you tell her.
Maybe it would be better for my relationship. Who knows, I may get lucky
You should tell her only if she asks for details, especially when it comes to the gory aspect of your service. You might be surprised to find out she is pretty tough in the mind. Either way, you're withholding information and not lying about it, so it seems harmless enough, so go with what your gut and your girlfriend tell you.