It would be great if life could be like a blackboard. After you write it with chalk, if you are not satisfied, you can wipe it with a blackboard eraser. Jiang Nan thought that his life should be a whiteboard, which was almost full of writing, but instead of using whiteboard pens, he used indelible markers. Although it can be wiped away with alcohol, the traces can never be removed. It may not be bad to keep it in mind.