Let your light shine before all.

 When Jesus tells us to let our light shine before all, he was not giving us permission to be proud of ourselves. Rather, he was saying that all of the abilities that we have came from God.

He demands that we use them for what is right.

As Paul said to the Corinthians in Chapter 4, What have you that you haven't received? And if you have received, why do you boast?

Telling us we should let our light shine, Jesus was telling us to use our abilities for him.