Most are five-minute exercises, but you may extend them to 15 minutes if you are comforatble with them. Try not to judge yourself for failing, or for doing them imperfectly, or for being distracted while doing them. Nevertheless, be willing to make an effort, and give them enough priority in your day to make the practice effective.
Thoughts are the bubbles of the mind, and fear arises out of thoughts.
Let silence come to replace it, but if that is not possible, let the next thought arise gently, and repeat the process. Thoughts often arise unawares, but giving thoughts over to fear is usually a choice. So is giving thoughts to Love. For five minutes at the beginning of your day, sit quietly in a quiet place. Think about the upcoming day, and the people you are likely to encounter.