Taking a penalty at a World Cup has got to be one of the most high pressure situations any footballer can ever have to face. The eyes of everyone in the stadium and millions more watching at home are all on you as you place the ball on the spot, take a few steps back, and figure out how exactly you plan on getting it past the keeper and into the back of the net.
If you happen to be German, it probably isn't such a big deal as they actually have a 100% success rate in World Cup penalty shootouts, but for everyone else, it must be an unimaginably nerve-wracking experience. If you score, you're a hero. If you miss, you might never live it down (though you may have a future in Pizza Hut commercials).
Whether it's during a penalty shootout or regular time, taking a World Cup penalty means that the hopes of an entire nation of fans are resting squarely on your shoulders. No human being is designed to deal with that much pressure, and it's only natural that players can sometimes crack, leading to some misses that will never be forgotten.