Book recommendations where one person chooses to distance themselves from their other half..

I'm looking for book recommendations (preferably romance) where either the FMC or MMC decides to distance themselves from the other—not because they don’t love them, but because they believe it’s for the best.

Maybe they’re afraid they’ll end up hurting the other person, or they think the relationship isn’t meant to last. It could be because of fear, guilt, difficult circumstances, or a heartbreaking realization that love alone isn’t enough.

Basically, I want something emotionally intense and heartbreaking, where the separation is painful, full of longing, and leaves you wrecked.