Squigly Squigly's Brain Teasers

Question:

What can you keep but cannot share and once you share it, you can't keep it anymore?

Answer:

A secret.

Try another Brain Teaser:

It's so strong, it does not break,
It's so powerful, it penetrates a lake,
Sometimes it's weak as a twig left out in the sun,
It's so wonderful it gives us the power to have fun.
What is it?