I can be completely alone with her.

On a cool winter's night, I can lay awake and listen to her drawing breath.

There is a rhythm -- A naturally occurring progression that  can lull you to sleep, or, keep you awake all night.

...

I can be completely alone without her.

Left high and dry, the panicked sensation seeps in. She's left from my life, and took everything with her.

She can be away for hours or months. Every second without her is lonelier than the last.