I'm not a fiend about "you must play this in Japanese only" by any stretch. I actually prefer the English translation in XIV instead of subtitles, which is rare for me.
But damn it, what we lose in translation sometimes.
Culturally, historically, the Japanese have been what you might call "sparing" with their outward emotions. Not that they don't feel the same emotions as any other humans; but love especially is a closely, carefully guarded thing, not to be gushed about day in and day out. To do so is to diminish the power of the emotion, to cheapen its value.
As it was put to me years ago, "I told you 'I love you' once. That means forever."
Now obviously, a culture is not monolithic, and Eorzeans are not Japanese. But the world and its people are unequivocally influenced by the culture from which the game comes. And in Thancred's case: we know he doesn't talk about his emotions. He almost pathologically avoids trying to feel them.
What he does do is act on them.
Here's what Meteion tells us Thancred says in Japanese:
守る, "Mamoru," in simplest terms, means "protect" or "guard." (と, a word particle, indicates that Meteion is quoting Thancred directly.)
"Survive," Thancred says in English. What's that mean? Great. Of course he wants you to survive. Doesn't he always?
See, "Survive" is an imperative in English. "Survive" is a command to you. Valid, yes.
But 守る, while it implies that command for your survival, is a declarative to himself. 守る means, I will protect you, whatever the cost: my own life, my own life essence, all of it. To protect you, I surrender to the unmaking of my body, aether, and soul, so that you will live.
Do you see how "Survive" warps the original meaning?
守る is Thancred's cri de coeur, torn from the deepest parts of his own soul. A man who would strangle his own life force rather than admit how he feels cries out in wordless desperation so powerful that it reshapes empty atoms into walkable ground under your feet; transmutes the nothingness of the void into the very air you breathe.
What 守る most deeply means is
And, to me, that makes all the difference.