Is he upset about this whole situation? A little, yes. But he understands it's for reasons beyond his control, and he's willing to give Elena the time to decide what she wants, because in the end, that's the only thing that matters. What Elena wants.

But he'd be lying if Damon doesn't still get under his skin. He knows what Damon's like, not just now but months down the line when Elena very pointedly kisses Stefan goodbye before they leave for Duke. He knows the way that Damon can goad at someone, and while he does his best not to let it get to him, there are times when he lashes out without really thinking things through.

(They're brothers. That's the point.)

This, unfortunately, happens to be one of those times.

He mentions putting his hands on Elena, trying to take advantage of her (it's not what he said, but it's what Stefan hears), and Stefan's reacting before he's even thinking, his fist swinging out and clocking his brother across the face.

If it connects, it's going to hurt like a bitch.

As far as he's concerned, it's worth it.