"I hear you," he says, even though agreement means very little when she knows he would do it again should the need arise and he knows she would not leave him behind anyway. Lightly said and not as serious as she would have wanted, he is certain even before watching her reaction. There is a certainty, ever present, in his belief in Astrid and Wulf; the solid reassurance their bond can withstand anything β even his most foolish decisions. The fall will not hit him because he has those who would always endeavor to catch him, just as he would for them.
Bren cannot be as dismissive as she continues, however; not because Astrid softens (she does not) but because he knows her sharp words to be honest. "You are both as good as I am, though," he retorts, not as an attempt to flatter but meaning it. Their master may have shown more appreciation for his skill a few times, yet that makes no difference. Anything he can do, Astrid and Wulf would be able to do as well. And maybe that is the thing, isn't it? He cannot do as well in the other things they can.
The idea of admitting that is embarrassing; as is the thought of just accepting he is not as skilled as his partners. A stupid wound to his ego, he knows, but it hurts nonetheless. "We're all talented wizards. I should be able to do more than that. I needed to prove I could do it. It's just β I don't want to stay behind."