I was lucky enough to meet Clay Christensen once when he came to speak at a company I worked at.
First he delivered a brilliant lecture on how companies repeatedly found themselves put out of business by new technologies, even after having made only decisions that actually increased their profits (his famous theory of "disruption").
Then he went on to talk about how easy it was as a driven, career-focused person--like most of the folks in that room--to invest too much in your career and not enough in your family. He pointed out how you can see whether your efforts in the office are paying off after a year or two, sometimes even shorter--while you don't really know whether you raised your children well for 20 years or so. Since so many smart people are addicted to feedback loops of quick success, he argued, that put them in special danger. You could easily spend year after year making choices that increased your success in your field, only to discover--too late--that you hadn't been paying enough attention to things that mattered more.
He was one of the best speakers I've heard, picking precise words and moving smoothly from topic to topic, but every once in a while he would hold up his hand, bring his fingers together as if he were gripping a pen, and then twirl his hand in a circle as if he were asking for the check. After the fourth or fifth time, he stopped and apologized. He'd had a stroke recently, he explained, and occasionally he couldn't remember the words he was trying to say unless he pretended to write them in the air.
A brilliant, humble man, whose essential goodness was impossible to miss.
May he rest in peace.