Know yourself and yourself. The art of war has a cloud, know yourself and know yourself, and fight every battle. Knowing yourself and yourself is a spirit of preparing for a rainy day. In today's society, whether studying, taking exams or working, we can't do without our accurate judgment. However, the essence is often hidden. At this time, we are required to have the spirit of opening up the clouds and reducing expenditure. Instead of simply clinging to superficial phenomena. Only in this way can we win every battle. (The arguments have all come out. Let's find our own arguments, which are purely original and can't be copied. )