After school today there was a note in my mailbox in the office. I opened it, and it was a letter from one of my graduating seniors. I've been her math teacher for two of her four high school years. In addition to telling me how much she enjoyed my classes and the like, she dropped one of the biggest compliments that I could hope to earn: she thanked me for teaching and demonstrating the importance of integrity.
That letter went instantly into my "rainy day folder", which I fortunately haven't needed to look at in quite some time.