PsychCentral has a list of 49 things to say to calm an anxious child. Even if that child is you. Some are more all-ages than others. But they’ll all work. You might try “I’m taking deep breaths” and “Let’s go to your happy place” with yourself. You might even try this:
35. “I see Widdle is worried again. Let’s teach Widdle not to worry.”
Create a character to represent the worry, such as Widdle the Worrier. Tell your child that Widdle is worried and you need to teach him some coping skills.
Most of it is CBT or CBT-esque. Enjoy!