Build a reduced-service plan and write it down before you need it, because you will never design one well at 7am with a queue forming.
Mine is a laminated sheet: on a solo day the menu drops to four items that can be made in under three minutes, the table service stops and everything becomes counter and collect, and a sign goes on the door saying limited menu today. Turnover on a solo day is about 60% of normal instead of 30%, and crucially nobody walks out angry because expectations were set at the door.
Second thing is a paid on-call arrangement. I pay one person 20 to be reachable on Saturday mornings whether or not I call. That has cost me maybe 400 a year and saved two days like yours.