The edge of the sword comes from sharpening, and the fragrance of plum blossoms comes from bitter cold.

If you don't climb the mountain, you don't know the height of the sky; Don't face the deep stream, I don't know the thickness of the ground. ("Xunzi")

Bee, you harvest flowers to make nectar. Who has worked hard and who wants to taste the sweetness? (Luo Yin)