I studied under Don at Dal for only a couple of years (over 20 years ago!). Even though my sax playing never really went anywhere, I know I still carry some of the lessons Donnie taught me. They were about music, but at the same time, about so much more. He always drew the analogy between playing music and having a conversation. You can know all the impressive things to say and just how to make them sound smooth and cool, but if you're not listening to the other people in the conversation, when you open your mouth, you're just going to sound like a jerk (and, more importantly, you'll actually be a jerk if you don't care enough to pay attention to the people you're talking to). Such an important lesson - in music and speech.
Another oft-repeated snippet that sticks with me: Donnie used to talk about how much he loved it when his little girl used to say to him, "daddy, sing me a song on the saxophone." I understood that this was something to aspire to: a young child (or anyone) hearing you play and thinking it sounds just as natural and heartfelt as singing. It wasn't just about how things sounded either, but about honesty and integrity.