The greatest heroes, the most successful and triumphant people, worry. I know I will fail. Understand what you fear. I'm so terrified of failing the final exam Wednesday morning. I mean the worst.
Nothing quells anxiety faster than action.
Often it takes a practical effort, like studying for an exam rather than worrying about it. Do this experiment for a month. Keep a diary and write down what worries you when it worries you. Whatever the worry, however small or large, log it. If you have the same concern repeatedly, write it down repeatedly.