There is a particular blindness that arrives with expertise, and it is not arrogance. It is the simple inability to reconstruct what it was like before you knew the thing. Once a concept has become obvious to you, the state of not finding it obvious becomes genuinely inaccessible. 

The consequences show up everywhere and are usually misdiagnosed. It is why experts write documentation that is accurate, complete and useless, because every genuinely difficult step is compressed into a sentence beginning "simply". And it is why we react to certain questions with a flash of impatience. The question seemed to miss something obvious, but obvious is not a property of the idea; it is a property of the relationship between the idea and a particular head, and the asker's head is not yours.

What makes this hard to fix is that you cannot detect it by introspection. So the correction has to come from outside: ask someone to explain back what they understood, watch where people actually stall rather than where you expect them to, treat every "stupid" question as data about your explanation rather than about the asker. The best teachers I know are not the ones who know the most. They are the ones who have somehow retained a working model of the person who does not yet know. So, as a reflection for today: when did you last check whether people were following, rather than assuming they were?