It's 6 am on Christmas morning, and Fleur Weasley is running wind sprints in the backyard of the burrow. Harry's no better, up early for a jog to try to push away the faces of those who won't be making the celebrations today.
The war has been over since Halloween, but the fear it brought still lives on. Fleur lost her husband, and Harry lost friends and mentors. They're both trying to run away from the guilt of making it through.
A Flowerpot fic where Fleur and Harry have continued to train like the war's still on because it helps them cope with not being good enough to save their friends. Training partners to friends to lovers, with probably some constructive outlets for their pent-up energy along the way.
I have a mental image of Harry introducing Fleur to Muggle Sunday League football (soccer). They join the team, and their teammates' coaxing is what helps them move from friends to lovers.