I am neither young or old. I guess that is what middle-aged is all about, but I don't like to think of myself as middle-aged because it sounds very mediocre. Middle-aged reminds me of middle ages, or medieval. Thus, I prefer to think of myself as medieval.
Being medieval - that is, neither young or old - I believe I can speak with some authority on why the old and young need each other.
Here is the lesson the old should impart to the young: "Be humble. Live as though you depend on God for everything, for in fact you do."
Here is the lesson the young should impart to the old: "Be hopeful. Live with the confidence and joy that the future is entrusted to God, for in fact it is."