You're a "glass half full" kinda guy, Dono? Quite natural due to your personal life experiences. What you say is true from your present POV. All things are subject to change as time rounds off the pointy corners.
However, I was referring to Jack's perspective of "home is where the heart is" POV. Jack has long professed to love his wife dearly and to have recently celebrated his 32nd wedding anniversary with sparks and fire. He doesn't appear to be of the same mind set as yours when it comes to his relationship. His experiences are not yours. (Assuming, of course, that Jack's love for his wife is not a troll.)
On the other hand, I understand your POV just as easily. All points of view are valid. It all depends on where you are standing at the moment.
If I chose to, I could say that I am envious of Jack in that he has found a partner willing to work as hard as he has to keep a relationship alive for that many years, and indeed he should be proud of his accomplishment.
But I'm not envious only because I know that with all the variables: jack's personality, mrs. Jack's personality, their location, their circumstances, all the possible twist and turns their lives have taken, are utterly beyond my ability to reproduce. Jack's life is his, a unique road he was lucky enough to find a travel partner to accompany him on. The same is true of any of us.
I suspect you're partly right; my life experience has reinforced the notion that nothing is permanent, and maybe that leads to a more stoic approach when things inevitably fall apart. But that view has also kept me from becoming bitter. The fact that I know things go bad also means I know they go good again, or at least go differently than today. It keeps life interesting. I may never get the pleasure of having one partner for three decades, but I'm sure I'll find another one to walk a while with me...
And to answer your question, I think the glass is neither half-full nor half-empty. The glass simply is. Until the moment when it isn't.