Chaoshan proverb, what does it mean that a dog's head doesn't eat the sky before it shines?

This means that the dog doesn't have any great ability, and then it won't say what sun it will swallow, or something like that.

There is a legend that Tengu eats the moon. Every August 15th, Tengu goes out to watch Tengu eat the sun. Sometimes Tengu swallows all the sun, but it opens Tengu's stomach and the moon comes out again, which may be the meaning of cutting Tengu to eat the sun, which means that the dog can't eat the sun.