"Appear weak when you are strong, and strong when you are weak." - Art of War
People that are strong get targeted by jealous people. The strongest always gets attacked when someone else wants the top spot. This has happened throughout politics, history, and high school gossiping. Appearing weak and telling "flaws" about yourself keeps you appearing human and weak. This keeps jealous people from attacking and allows you to save time and energy for real enemies.
Appearing weak also make you a wonderful temptation for those that real hate you. People are like sharks and they attack when they smell blood in the water. If you do not believe me, then think back to high school gossiping. It can ruthless sometimes! People that really hate you will come out of the wood work on the attack when they smell blood, which is why you want to appear weak when you have the firepower to take them down.
Appearing strong is important to keep attacks at bay. Sharks and people attack when they smell blood in the water, which is why you want to trap them into attack you while you have muscle to deal with them. However, there will come a time in everyone's life when they do not have the fire power or high ground. This is when appearing strong will pay off. People will not attack if they think it will cost them greatly. Appearing strong when you are weak will keep enemies guessing about how much attacking will cost them. The key is to put up a smoke screen they will believe or in a way that they will not want to call your bluff.