Ever been on a long walk, and been walking a while, and realize that walking's just too easy? So, you start a light jog. And that's easy, too. So, you start skipping. And that's easy, too, at first. But then your foot starts to slip a bit. You catch yourself, but you keep skipping along. But then you trip and fall. You're still on your walk, but you get up, dust yourself off, and realize you need to just walk for a while, and look out for things that might trip you up.