I believe that the stuff they teach in most martial arts schools are too weighted on tradition. You have to  defend yourself in all ranges. Remember we can not always pick the range in which we fight. We have to defend ourselfs from all ranges. Most fights occur when we least expect it. A sucker punch, multiple attackers and being attacked by a weapon. These are just some scenarios. Are you prepared for the unexpected or are you just going throught the motions. The most effective way to defend yourself against a knife, is to have one yourself. If you don't have a knife you need to find a equalizer of some sort. Because  a knife can do you serious damage. You should always practice with a wooden knife or a magic marker. This way you know how good you with defending against it. If you have marks all over yourself from the magic marker. Well, you need to improve your reflexes before going any farther. Dan Inosanto, The man that Bruce Lee told to carry out his art says, you have to have reflexes before you learn any techniques with a knife. A Good Book, I Recommend To overcome your fears is, Click this Link here!  Never Freeze in A Fight, Check it out. You won't be disappointed.