The potion may have effects less severe than damaging. I know that sounds cryptic, but it will make sense before the end of the story.

And thank you. One thing I sometimes struggle to convey in my H/D fic is that Harry does love Draco, because I also like a Draco who's more IC (so somewhat bratty, selfish, and petty). Here, though his love began as irrational obsession, it's moved beyond that, so I need a way to distinguish the two. I'm glad it works for you.