James 1 v 22: Be doers of the word, and not hearers only, deceiving yourselves.
For 4 weeks now a solar outside light, that comes on when it detects movement, has been lying on my dining room table. My husband shows anyone who visits how brilliant it is (pardon the pun) and how well it works. But, its of no use on my dining room table! It should be mounted on the garage wall facing the driveway for use in the night, but.....
Its just a useless piece of plastic and metal, making an unusual dining room table ornament (not!).
God's word illuminates!
This is a little like reading God's word, thinking its awesome, and then not applying it to your life. Your life does not change. Your inner light, powered by the Son of God, if not exposed to the word and then converted into practical God fearing action, will not change your soul. Your Christianity will just be a fish sticker on the bumper of a speeding car - not much of an example! You won't be growing.
So, as the verse above says, don't only be readers of the word - be also doers of the word. Apply God's word. In this way your life grows closer to Christ and inner light shines brighter, drawing others to Christ.