Missing a day is not a crisis.
A sensible approach
Return to your normal schedule at the next usual time. Do not double up, since the page says not to exceed the label serving.
Make it less likely
Tie the capsule to a meal, keep the bottle visible, set a reminder, and note misses in your log so you judge the trial fairly.
Educational note: This guide is general information based on the Quiet Nerves page. Statements have not been evaluated by the Food and Drug Administration. The product is not intended to diagnose, treat, cure or prevent any disease. Individual results vary.