Riddles and horror stories

Riddles

Once in a minute, twice in a moment, never in a thousand years. What am I?

I can't be seen, I can't be touched. When you see me you can't have me forever. I can give you anything you want, but when I'm gone everything is normal again. What am I?

If you throw me out of window you will leave a grieving wife. But if you bring me back in the door, you will see someone giving life. What am I?

Don't forget to comment what you think the answers are.