Answer:
There are millions of me. I am very small but when moving fast I am deadly.
A man went to a place on thursday on his horse, he came back 3 days later on thursday how is this possible?
When young, I am sweet in the sun. When middle-aged, I make you gay. When old, I am valued more than ever.
I walked and walked and at last I got it. I didn't want it. So I stopped and looked for it. When I found it, I threw it away.
What has roots as nobody sees, is taller than trees. Up, up it goes, and yet never grows?
I’m grown from darkness but shine with a pale light. Very round I am and always a lady's delight.