This story was inspired by Psalm 31, and while it is almost entirely film-verse (implicitly for Prince Caspian and explicitly so for Dawn Treader), the Dawn Treader section uses book timelines/dates for things like how long Edmund is aboard the ship. Any character(s) you recognise belong to C. S. Lewis.
Be my rampart, my fortification
You've never thought to test your boundaries, to invest in someone at the emotional level. The whole idea, knowing you'll lose them one day, whatever you do, frightens you. You know Aslan's modus operandi well enough by now to know he won't keep you here any longer than necessary and, knowing that, how can you attach yourself to another person in that way?
But it isn't a conscious decision, in the end, because falling in love never is. And you don't let yourself think about what might happen to you when you lose Caspian. You're in love with him, deeply in love and, with his encouragement, you let your feelings for him deepen further until you can't quite imagine what your life without him will be like. And when the time comes when you must imagine it, when Aslan decides you must return home, nothing you try makes any difference. It's far too late to change a thing.
For you are my strength
On your return to England, those closest to you find you to be a changed person. Those who knew you before Narnia are particularly aware of this. Stubborn, to a point almost beyond credulity, because you have to be in order to hold on to the one you love while trapped, away from him, in your own world. Steadfast and faithful, through everything, to the end. The reward for your faithful heart is the fulfilment of your wildest dream, bringing you back to Narnia with Caspian still young and alive. You're almost possessive of him, in the way people are when they have someone precious they cannot bear to lose. You know you can't stay, have known since you coughed the water out of your lungs on the deck of the Dawn Treader your time with him is finite. But your love for him is so fierce, and you're so glad to be back in his arms again, that for a short while you're disinclined to care.
When you do take a moment to consider things you remember how, last time you were here, you made a connection with Caspian that's stronger than anything you've had with anybody else. You decide you want and need him enough that you're willing to endure what's in store for you when, as is inevitable, you return to your own world. You'll do anything, for him, no matter how much it hurts. How can you do different when you love him this much?
It's clear to anyone with eyes what you are to each other, because he isn't subtle and therefore you can't be. Over the next few weeks you let him become necessary to you in a way that's dangerous. Both on board ship and off, he proves what you are to him day after day without words: simple things such as sharing a bed, or the slide of his tongue against your own.
You will lead me out of the trap that they laid for me
Then there's the day he saves you from the Sea Serpent, tearing across to dive between you and the Serpent like a guardian angel and bringing you down to the deck beside him. He's never been good at hiding emotion, and everything he feels for you is clear on his face. You're so sure of him that when the thrice-damned Witch tries to tempt you, it's easy to resist.
She offers to make you her King, but you are a King already. She offers you more, but there's nothing more you want if you can't have it from, and with, Caspian. She holds no power over you any longer; this is something Caspian, and your relationship with him, shows you. Caspian, in whom you have always found acceptance and understanding and who, in the short time you've been here with him, has saved you from yourself time and again.
For you are my strength and my refuge
