"It's failure to prepare mentally and failure to take practicing penalties really seriously." This is Ken Bray's explanation for England's dismal performance in penalty shootouts. England are successful in only 17% of their encounters, compared to Germany's impressive 80%. Bray is an expert in the science of football, and he has studied the physics as well as the psychology of penalties and analysed the statistics. The result are three steps to ensure a perfect penalty, which he explains in this video. You can find out more about the science and maths of football in Bray's Plus articles on football.
the possibility of inaccuracy is lessened if the shot is kept low, simply because you are less likely to go over the cross-bar. Many failures are because players aim for the known unstoppable area in the top corner of the goal which although the best place because of its size and position is vulnerable to inaccuracy even for good players. Low confidence will also cause many players to aim for the bottom corner for this reason.