"What?" he asked innocently. "It's very difficult to concentrate during sex, and I can still manage. You should be proud of me."
This was the kind of magic, he like. No like wasn't strong enough. He loved it, love the feeling of learning and trying something new. He took the wand out and repeated the wand movement first, as if imprinting in muscle memory, and then he did it again, this time he cast the spell as he touched his body.
He could feel the sensation that Snape described, but he also knew that feeling it didn't mean perfection. He cancelled the spell with another tap and then looked at Snape. "So how did I do?"