Have you been faithful at what you know best as a worker? Or you have seen yourself doing what you don't know, leaving behind what you know best?
The pencil knows itself as an inscriptional tool. The eraser also knows itself as a cleaning agent. It will be however ridiculous for the eraser to argue to swap functions with the pencil. It must be where it is and do what it knows best!
Who do you know who you are? That answers your purpose of existence. Stay in your well known closed Circuit and you will spark a Direct Current across the Potential Difference of with your Key! Love you more!