Good tests => Good Teeth
A bunch of us at work are reading Kent Beck's Test-Driven Development. From today's reading, my biggest takeaway was "To keep your teeth healthy, retroactively test before refactoring"!
Confused? Here's his explanation: "Write the tests you wish you had. If you don't, you will eventually break something while refactoring. Then you'll get bad feelings about refactoring and stop doing it so much. Then your design will deteriorate. You'll be fired. Your dog will leave you (Huh?). You will stop paying attention to your nutrition. Your teeth will go bad. So, to keep your teeth healthy, retroactively test before refactoring."
Hope this will motivate all you software developers to write more tests ;)