Keep learning from your customers is really a poor achievement. A person who is really positive about improving himself and the world around him should be aware of this secret: every person you meet in your life, even the humblest or the worst ones, have something to teach. Something you can learn, to reshape yourself (your soul, your mind, your entity) in a better and improved way.
Try it by yourself, in the worst possible scenario. Think about the worst person you've ever met in your life. Think about the time you spent with him. I'm pretty sure you'll find out something you're doing better (or something new and exciting) because of him. And no matter if it's just a detail, a little spot: it's now one of your improvements.
So go on with your lives, and remember to see behind every face, every handshake, every human - the chance to learn something.