If your mind is preoccupied, a good way to improve your concentration is to focus on your physical sensations. Massaging the following points, called "switching on" points, may help you with that :
The "tuning in" technique can also be helpful :
If a particular matter or aspect disturbs your attention, instead of trying to obliterate it (which rarely works), take a small break and allow yourself to put your full attention to this aspect. If it is stressful, for instance a specific jump on the course, use the following technique (called ESR : Emotional Stress Release) while contemplating fully the disturbing item/jump/situation... Notice how you feel at the same time. It may take a few minutes to feel better about it. Then go back to what you were doing, you will probably find it easier to focus now.
If this isn't sufficient, a Touch for Health® private session is a very powerful way to regain calm and focus.
More info : http://www.touch-sport.fr/en/