If the wick within the lamp is small, the light will also be small. If the wick is big, the light also will be powerful. Similarly if the Jiva (individual soul) is pure, if he practises meditation, the manifestation or expression of the Self will be powerful.
He will radiate a big light.
If he is unregenerate and impure, he will be like a burnt-up charcoal.
The bigger the wick, the greater the light. Likewise, the purer the soul, the greater the expression.