A top-level, charismatic performance requires good concentration skills. Concentration involves paying attention to what you are doing – losing yourself in your task.
Concentration is one of the crucial prerequisites for a good practice session and must be constantly monitored. You will only achieve results if you are concentrating – unfocused practice may even set you back. (You may, for example, repeat mistakes until they are in your muscle memory.)
Unlike relaxation, there are no techniques for practicing concentration. You will best learn it simply by concentrating every time you practice. The tough nature of this kind of work is, of course, problematic. It is easier to let your mind wander than to focus properly on what you’re doing. On the other hand, a shorter session of good practice generates better results than a whole day of unfocused work.
You should also remember that a period of focused work needs to be balanced by sufficient recovery time.