I used to write inspirational quotes on a whiteboard in our kitchen every morning. For some reasons I had forgotten to renew the last quote for a few days. Today, I wanted to write a new quote but it was hard to clean the whiteboard after several days. It was as if my writings were printed there forever. I thought that should be avoided next time, otherwise I cannot use the whiteboard any more. This simple occurrence reminds me of the old thoughts and habits in my mind that are difficult to get rid of if I forget about them and let them be.