Ron was almost relieved when she took his journal so he didn't have to try and think of what to say to his sister anymore. And when she moved towards him, his arms went around her so quickly he realized he'd just been waiting for her to move into range. He let his eyes close and dropped his head to press his lips to her shoulder, just resting against her for a moment, as though he had to catch his breath.
After a few deep breaths and some stretching silence, Ron tilted his head back and let it thunk against the stone behind him as he looked up at her. "Dunno. Bit better now, though."
What else could he say? He'd seen red. He'd gotten angry that his best mate was fooling around with his little sister and the urge to keep her little and young and innocent or something had taken over. Much as he didn't want to think about Ginny and Harry doing the sorts of things he did with Lav, he couldn't deny anymore that they did. At least some things. Harry had said as much by refusing to make the denials Ron had asked him to.
But even now, only moments after the arguments had finished, Ron knew he'd over-reacted. What was he supposed to do, though? Say congratulations? Say sure, do whatever you want to my sister, I don't give a shit? He did give a shit. He wanted to take care of her, make sure she never got hurt, and even if he knew Harry was a good bloke, the best, really, it didn't change the fact that Ron wanted his little sister to remain his little sister.
"I might've, uh. Over-reacted. Just a little," Ron admitted, mumbling as he spoke.