Proverbs 27:17

As iron sharpens iron, so one man sharpens another. – Proverbs 27:17

It takes iron to sharpen iron. Sharpening a knife requires iron at least as hard as the knife. Once sharpened, a knife is bright, sharp, and ready for much more productive service.

I'm "working" in the craft world right now and while it is not iron.... creativity sharpens creativity.  Your peers influence you.  Peer pressure does not stop when you're in school.  Your peers pressure you at work.  Your peers pressure you at church... etc.  So you want to choose what is going to sharpen you.  You will be shaped by one thing or another, don't you want to be a sharper grade of iron to be used for the productive service of God?  

Rom 9:21

Hath not the potter power over the clay, of the same lump to make one vessel unto honor, and another unto dishonor?

I want the Potter to be the power over how I am to be shaped and for what purpose he wants to use me.  To sharpen me as iron, to refine me as silver to shape me as clay.