Perhaps you are nervous about an upcoming situation, and your mind keeps going over all the things that could go wrong. Instead of letting a barrage of negative thoughts take over your life, create a list of positive affirmations to counter the negativity. Suppose you are nervous about going to a party where you will know no one except the hostess, who will obviously be very busy. Repeating a positive phrase like I will be relaxed, sociable, and have a really fun time fifty times a day every day before the party (in five sets of ten) will create an expectation in your mind that your brain will be happy to fulfill.