Answer:
You speak this when you are being sincere.
The thinkers usually hold this body part
What has to be broken before you can use it ?
Small, containing light, You'll need it in the dark, It will provide that spark, and shine into the night. Will light up any pyre, 'Cause it can help make a fire.
Come up and we go, Go down and we stay.
In birth I spring forth, in life I unfold. In death I wilt and die, but rebirth restores all.