I like the previous answer to concentrate. Also, you can try a few various things. #1, you could make a list of all the things that are on your mind and prioritize them and alot times to do each one according to their priority to you. Clear your mind so that when you act, you act. After acting, you can attend to your to do list. Make good progress so that you do not have to worry while you are acting and give it any thought. #2 be prepared in whatever way you need to prepare you to act - prepare a snack, have all your supplies with you, clear your mind, clear your schedule, arrive early, and limit distractions and - break a leg!