When people come up and thank you, consider saying: “I appreciate you saying that. What did you like/notice/appreciate the most?” That will quickly get to the essentials of what they are taking away, which commonly is less about what you said and more about what they got. This is terrific feedback for us!
Also, whenever you finish any presentation, however short, ask yourself: “What did I do well and what is one thing I might consider doing a bit differently next time?” We can only build on our strengths so don’t be the hardest judge of all.