Answer:
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.
Walk on the living, they don't even mumble. Walk on the dead, they mutter and grumble.
I can move even when you are still. I can be one or many.
Being able to interpret the letters on this screen proves that you have this quality.
I'm not man's best friend, I'm their enemy, I can mark your end, yet you do not see me, I am very small, but very tough, If you have me, then you have it rough.
The warmer I am the fresher I am.