Answer:
I make you weak at the worst of all times. I keep you safe, I keep you fine. I make your hands sweat. And your heart grow cold. I visit the weak, but seldom the bold.
A hole in a pole, though I fill a hole in white. I'm used more by the day, and less by the night.
Glittering points that downward thrust. Sparkling spears that never rust.
Turns us on our backs, and open up our stomachs. You will be the wisest of men though at start a lummox.
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.