When a sailor uses a star to navigate by, it's called a lodestar. The most commonly used lodestar is the bright and easily spotted Polaris, also known as the North Star.
Navigating on a clear night at sea, you'll need a lodestar to guide you so you always know what direction you're going. Something that similarly guides you through life and its tricky decisions can also be called a lodestar. This might be a mentor or some other person who helps you figure out which direction to go, or a guiding principle. Lodestar, "star that leads the way," uses the "way or course" meaning of lode.