Let's be honest—this trope is a mood. Healing after 'the one that got away' leaves for good hits differently than a standard breakup arc because the door is slammed shut. No hope. I've noticed it often follows a specific rhythm in fiction: first, a hollow numbness where the protagonist goes through motions (work, fake smiles, empty rooms). Then, the narrative forces a confrontation with the past, not through reunion, but through objects, places, or new people who mirror old wounds.
What's fascinating is how the 'healing' is rarely clean. In 'Normal People', Connell's grief after Marianne leaves for Sweden isn't about grand gestures; it's in the quiet disintegration of his daily life, the inability to write. The story suggests healing begins only when he stops trying to replicate their bond and instead sits with the absolute absence. Similarly, in many webnovels with a 'left forever' tag, the healing is tied to a brutal identity shift—the protagonist who was defined by the relationship has to dismantle that self entirely. Sometimes it's ugly, involving self-destruction before rebuilding.
The most satisfying versions for me aren't where they 'move on' to a better love, but where they build a life that's structurally different, where the faded love becomes a permanent, quiet scar rather than an open wound. The happiness afterward feels earned precisely because it doesn't try to replace what was lost.