The spiritual principle this has taught me--one of them, anyway--is what Paul so convincingly describes in 1 Corinthians. He writes:
...The head cannot say to the feet, "I don't need you!" On the contrary, those parts of the body that seem to be weaker are indispensable...If one part suffers, every part suffers with it.
~ 1 Corinthians 12:21,22,26