Answer:
What is it that you must give before you can keep it.
I can run but not walk. Wherever I go, thought follows close behind.
Tool of thief, toy of queen. Always used to be unseen. Sign of joy, sign of sorrow. Giving all likeness borrowed.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
Who spends the day at the window, goes to the table for meals. And hides at night?
It weighs next to nothing but no one can hold it for long. What is it?