The average size of a worry stone is three centimeters. When using them, the stone is held between the index finger and thumb while being softly rubbed back and forth over the stone with the thumb. It’s believed that stress can be eased by rubbing one’s thumb back and forth while holding a stone. Calming stones have a remarkable effect on the brain and thoughts, reducing anxiety and tension and calming the nervous system. Promote positive thinking to keep you grounded.