"For a clearer complexion"? Lolita cited that as a reason, too! (The Annotated Lolita 137).
Sometimes it's just as simple as sitting at a cafe, talking across a table, watching him gesticulate with his hands as he talks. And I fixate on one leg, half-bare in his shorts. Looking at that bare skin, golden, layered with soft hair, strong with muscles, I think I really need to wrap my legs around his. And I say, "Time to go."