James returned the smile, though it was triggered a bit more by watching Harry fuss at his hair than what Harry was saying. Once the whole of it properly registered, James reckoned he could put breakfast off a little. Something sort of unfurled beneath the curve of James's mouth, something a little cautious at traversing unfamiliar territory. "They don't really make a reliable potion for... that."
He meant the feeling desperate, and from the way he said it, he reckoned it was clear enough that he wasn't so much talking about the hangover. James, after all, had plenty of experience in being pushed away by someone he cared about. Plus, it was entirely possible that their taste women overlapped in more areas than just hair colour.
And of course, James reckoned that Harry had plenty of leeway to change the topic, to keep it about the headache and the stomach instead of the heart.