Answer:
When young, I am sweet in the sun. When middle-aged, I make you gay. When old, I am valued more than ever.
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
Round like a dishpan and smaller than a bathtub. But the ocean can't fill it. What is it?
I am the outstretched fingers that seize and hold the wind. Wisdom flows from me in other hands. Upon me are sweet dreams dreamt, my merest touch brings laughter.
When they are caught, they are thrown away. When they escape, you itch all day.
When is it bad luck to see a black cat?