What does "iron sharpeneth iron" mean?

Great questions brother! I would say whoever challenges you sharpens you. The verse says, as iron sharpens iron, one man sharpens another. It doesn’t say “friend”. It says “man” which means all mankind. It doesn’t exclude those who are not friends. Those who challenge me the most are the ones who sharpen me the most. The raw truth is required for this to take place. Lies hinder and hide this process. God uses everyone and everything to teach us the lessons he wants to teach us and refine us into who he wants us to become. Both now and on judgement day, what defines us is what happens to us in the fire. The same fire of judgment affects the righteous and the wicked differently. A great example of this is Shadrach, Meshach, and Abednego. When they were thrown in the fire, their chains fell off. Their refinement brought their freedom. But the same fire consumed and destroyed those who threw them in. Sharpening involves friction and friction turns into fire.