A humble person is a person that sees no intricate self importance to himself. His role in life is an entity of importance only when he is together in a social structure. Together, with his society, he shares his life with others. A grape is also something that improves when it is squeezed. Can you compare the worth of a cluster of grapes to the worth of wine that was made from it.
Wine is a much more valuable commodity.
Only when the grape is squashed does it reveal it's true excellence. The same is true of a humble person. Only under pressure can we see the true worth of a person. How many people stumble and sway due to pressures. A truly humble person is able to come out of a difficult situation unscathed.