Share? I'm Gone!

When you have me, you feel like sharing me.
But, if you do share me, then you won’t have me.

What am I?

Answer: A secret! 

Full To The Top

I'm sometimes full, but I never overflow.
What am I?

Answer: The moon! 

One Color, Any Size.

Only one color, but not one size,
Stuck at the bottom, yet easily flies,
Present in sun, but not in rain,
Doing no harm, and feeling no pain.

What am I?

Answer: A Shadow!

Gone With A Sound

Say my name and I am gone.

What am I?

Answer: Silence!