I want to add one thing to this post. I have seen every player, including champions miss relatively easy shots. Why? Because they lost their concentration for a moment. They got lazy! If you concentrate on hitting every shot the absolute best you can, you will rarely, if ever, miss an easy shot. That alone will make you a better player.
And another thought for you. Quite often good players (and some not so good) miss position when shooting at an easy shot. It happens a lot more than it should. The shot is so simple. How come he (or she) got so far out of line? Yes, they make the ball, but end up bad on the next shot. Why did that happen? Now you know. They failed to concentrate on hitting the shot exactly right. THEY GOT LAZY! Never happened to you, right?