Koroganu Ishi ni Koke Musazu " A stone that rolls gathers no moss."

For the Japanese, moss is something to be admired. Associated with beauty, moss grows rocks and in pathways of old temples in places like Kyoto. Yet the stone that continues to tumble will never have moss. So this expression is often used to admonish others to stay put, to continue on in the same job. Ironicaally, this expression is also used by somme Japanese to mean the very opposite, i.e., the meaning understood by Americans: keep moving or you'll get old.