転がる石には苔が生えぬ

[Korogaru-ishi-niwa-koke-ga-haenu]

Literal translation:

Moss will not grow on a rolling stone.

Meanings:

(1) Those who often change jobs or residence will be unsuccessful.

(2) Those who move around actively can keep their abilities from declining.

English proverb with the same expression:

A rolling stone gathers no moss.