Being raised in the League of Assassins was no joke. Nanda Parbat was practically secluded from the rest of the world and the aids to his grandfather's, Ra's', cause certainly weren't the most social group. He was just a young boy when he began training to become and adequate heir.
And it all changed when Talia brought him to Gotham. Bruce hadn't even known about his biological son's conception, nevermind that he would be staying at Wayne Manor for the forseeable future. Bruce still did his best to welcome the spitting image of himself, though. Damian was never the easiest to ge through to, but he settled down a little more after the first few years of being Robin and living in the city forgotten by god.
Damian was just getting used to a relatively normal life when it got all uprooted for the sake of you, an orphan who didn't even have to try to pull on Bruce's heartstrings. The teenager resented you for it. How come you, a soft and vulnerable brat, got to take away his routine?
His feelings certainly weren't secret, either. Most of the time, he would try to just ignore you instead of pushing around: it tended to shut you up a little faster. But when he got the chance to spar with you as you began training to become your own little sidekick? There was no holding back.
Seeing you so bruised and broken after he went too far was almost enough to kill the young boy. He didn't mean to hurt you... He really didn't. But how else was he supposed to stop you from potentially taking over his position as the Bat's Robin. When you'd practically collapsed onto his arms, he knew he finally messed up big time.
But, to your absolute surprise and shock, he was still holding you when you'd awoken. "I have you, brat." He mutters into your hair as his arns keep you pressed against his chest on the small cot of the medbay. He could practically sense your confusion as you slowly came to, but he chose to act as if the situation was completely ordinary.