One thing I've noticed about these TAR broadcasts is how easily and nonchalantly these pro's pocket balls while chatting with the host. If some of these shots appeared in a televised match the analyst would inevitably say something like, "This one's a real tester. In a pressure situation like this, I'll give him a 50 - 50 chance of making it." It seems when they're just shooting around, they make these same shots a whole lot more often. So let's put the cue-ball at the head of the table 4 inches away from the short rail and half-way between the center diamond and the next diamond either tp the right or left. Let's put the object ball right smack on the foot spot. How often does the average pro make this shot while practicing and how often does he or she make it in a pressure packed tournament match?
The first thing you need to realize is that pressure is a good thing. You need pressure in order to compete at your peak level. This is not just my opinion, this is a proven fact. In sports psychology I think it is referred to as the optimum level of arousal. To use a analogy, think of pressure to be like water, too much of it and you drown... Too little of it and you die of thirst. You made a statement saying that it seems when the pros are just shooting around, they make difficult shots a whole lot more often. I don't think that is the case most of the time. Next time you are at a tournament or watching some pros match up, watch them warm up and see for yourself how their performance compares to when the match starts. Pressure brings you to that optimum state where concentration becomes more intense. Most records, in every sport, are broken under pressure situations.
Just knowing that pressure is required for peak performance will help you to relax when you start to feel the nerves. Everyone feels the nerves too when they are competing and under a stressful situation. While Niels post is not entirely incorrect, it leads one to believe that all stress can be eliminated with the right techniques and to be a pro or to perform at a peak level, elimination of pressure is required. I know that is not the case. Believe me, the pros feel the stress... you are not alone... and remember you want to feel the pressure because it is good.
Gene is right. Pressure is less with the pros. They do learn how to manage it better to keep it from growing into a pressure so great that, to use the analogy again, they drown. One of the ways to do this is with a mental pre shot routine. Some of the best have a consistant routine that they have practiced over and over so that it is automatic to them. This focused practice and consistant practice of his routine is going to make it easier for him to think the same way while preparing for the final shot at the 9 to win the US open as he does for a routine shot in any tournament. His thinking process will be the same. Not just any old routine is good enough either. The routine should be organized to guide you from left to right brain activity. Having a good routine that you follow will keep you focused on the process and not worry about results. An amature will not have a consistent routine that is properly organized that they use on every shot. They will drift off into thoughts about what happens if they miss this... how great it would be if they could make this etc.
I don't want to give the impression that Neil is entirely wrong either. There is a lot of truth to what he is saying. Pressure can be managed better if you can identify the source and identify how you can think differently about certain triggers that cause you to put pressure on yourself. Perhaps you find that you are putting undo pressure on yourself because of a perfectionistic attitude that causes you to create unrealistic expectations... If so you need to change that. But recognize that you will never eliminate the pressure, nor do you want to.
PRESSURE IS GOOD!