I sent this to a friend I used to have a couple years ago. I realize the modifier is ambiguous. You can figure it out.
I loved your devotional tonight and I sort of went off on this tangent of thought after you talked about letting your light shine, and how "let" is not an aggressive verb (I don't think you used the word aggressive, but that was the point). I remembered that we had discussed the verb "let" in my linguistics class, so while Mary was rearranging the room again I looked at my notes.
Morphological Merging is when two forms of a morpheme change and merge together. One of his examples was "let". Way back in Old English, or maybe just Middle English, there was a verb, "laetan" which meant to allow, and a verb "lettan" which meant to hinder or stop. Eventually, the two merged into "let" and now we've dropped the meaning to hinder or stop. Occasionally you will come across it (i.e. legal documents, "without let or hindrance" or in the scriptures---Romans 1:13) but for the most part we take it to mean allow.
So when Jesus says "Let your light so shine before men" He's saying allow your light to shine, don't hinder it in any way (which I think is an interesting coincidence). The word "allow," at least for me, implies being willing for something to happen, usually something that is a natural occurrence but that we really do have control over if we want---allowing your children to date, drive the car, take music lessons. Allowing the cat to go out of the house. Allowing your light to shine. It wants to shine, it's a natural occurrence (as long as we're living righteously), all we have to do is allow it. Let it. Wu-wei, passive action by not-doing, being in harmony with the universe and the way things should occur. Letting. Let Christ into your life. Let Him be your life. I think it's incredible.