Some mantras I recall a lot, to help keep on the rationalist straight-and-narrow and not let anxiety get the better of me:

1. What's more likely to do you in?
2. Don't let the perfect be the enemy of the good.
3. Equanimity in the face of small threats to brain and body health buys you peace of mind, with which to better prepare for serious threats to brain and body health.
4. How have situations like this played out in the past?