Because of your skill with an instrument or music, the moon will always aid your appearance with such? Maybe it's more cryptic advice than a fortune.
This.
The "moonlight" could be a metaphor also, but Neon's idea seems the most logical.
As for the metaphor, I guess it could mean that if you choose to be a musician, you could achieve fame("The moonlight(aka limelight) never misses an appointment(will never fail to shine upon you)").
Too lazy to explain the rest/in greater detail.