1. Make mistakes -- don't think that's a good advice;
2. Be self-confident -- self-confidence has very little to do with your ability to speak English -- 安河内哲也先生 should know that Be proud of Japanese English -- be proud all you want, just make sure people understand your katakana English;
3. Speak in a loud voice -- people are who they are, they won't change just because 安河内哲也先生 tells them to.
I believe that Yasukochi 安河内哲也先生 means good, he does care about English education in Japan, his advice is well-intentioned but not very practical.