Let me explain. There's no such thing as an unstoppable attack, nor an impenetrable defense. Any attack can be foiled (literally) with the right parry. The trick is to use the right move at the right time, and that's been my bête noir. You can't know what the right move is until you see what your opponent is doing, and that means you have to observe and react very quickly.
Recently I had a bout with a relative beginner. At one point she launched an attack. Since she expected me to parry, her attack included a circling movement intended to evade my parry. And I expected that, so I executed a viciously fast, perfectly precise parry-four-counter-four: a simple parry followed by a circular parry. The circular parry was to pick up her blade in case she succeeded in evading the first parry.
And it didn't work. She hit me, poink, right on target. While I was showing off with my fast, precise parries, she was still executing her circular attack, so wide and so slow that it went all the way around my fancy tight maneuvers, and hit me well after I was done.
Had I actually responded to her attack, I could have stopped her easily. There was plenty of time. But instead I just chose a defense I hoped would work, and it was completely wrong. Even with that slllloooooowwww attack, I was unable to respond appropriately.
So now I'm wishing I hadn't so thoroughly ignored my kids' video games all these years. Maybe my reflexes would be better if I'd had more practice! But I'm working on it--it's never too late to learn. Someday, I might even be good enough to handle a complete noob!