Achilles' heel

When I was reading the book titled " A Dictionary Of English Idioms ", I had come across this phrase, Achilles' heel. Apparently Achilles is an ancient Greek name. It must have something to do with the Greek mythology or something that was really happened, and then constitute to some historical facts. The dictionary defines the phrase as " fatal weakness or the only weakness "( I translate completely from the Chinese definition). I googled this phrase after finding myself interested to know more. According to Wikipedia, the meaning is almost the same but it provides extra articles to explain more about Achilles.

Classical myth attributes Achilles' invulnerability to a treatment of Ambrosia and burning away of his mortality in the house fire except on the heel, where he was held by his mother Thetis. There is another rising myth stating that it is actually his mother dipped the infant Achilles the river Styx which could confer immortality, holding onto him by his heel. However both the myths end up by relating Achilles' death to his heel wound caused by a poisonous arrow which couldn't hurt him in the other body parts. I was then satisfied by the definition given "An Achilles' heel is a fatal weakness in spite of overall strength, actually or potentially leading to downfall ".

Okay where's my Achilles' heel? Which one of my characteristics is referring to it? I guess it would be my lack of perseverance, being a procrastinator, low general knowledge, speaking louder in words than in actions, afraid of my own's shadow, absence of mind due to the distractions around me and the most fatal one towards a doctor-to-be, that is communication skill. I write more than I speak. I can write using rhetoric in Chinese but speak in an opposite way. People think I'm a dull guy who is non-sociable when they speak to me. In fact, I don't think it is necessary to speak much. I'm emotionally rich in the written words. Therefore I'm worried when it comes to speaking which is all-in-English later. I'm packing myself up, reloading the language bullets and polishing my tongue now. I hope it works :)