What are marines conditioned to?

So I was talking to a friend today and she expressed her concern about me getting hurt. She brought up the fact that I'm a single mom who's been happily living the last 3 years alone with just my job and my child. Also how I'm a ready made family who already can survive alone, and have a lot of love and fight in me. She mentioned that she doesn't doubt he loves me but that he may just want someone he loves and can handle to be there when he his but he may never really be as concerned as I am. Not because he doesn't care but because he's conditioned not to. She said that marines are conditioned to things like loyalty, leaving without long goodbyes, and not getting too close. Now loyalty, discipline, and other traits sure I can grasp that. But the things that are more personal and emotional.... Im not so sure. Could it be that some of the things we love in a person are not how they truly are and feel, but rather how they are conditioned to be?! I'm not buying into what my friend said, I love my boyfriend and if he feels like I'm STRONG enough to handle everything the marine family/spouse goes thru... then I say hell yeah! He clearly loves me and my son and is a FANTASTIC person all around. We have been dating almost a year. We were best friends who were secretly inlove before he joined the marines (almost 10yrs ago) and we're still inlove now and it just keeps getting better... but could some of what shes tryin to tell me even remotely close and if so... what kind of things are they conditioned to personally or emotionally?