1. Try not to panic - I tend to go in panic mode but that doesn't do much good. So, relax. You'll survive.
2. Call in the back ups - Having a back up plan is needed. You can ask even if they can only work a few hours, it'll be a help.
3. If they give you adequate time, prepare. Think of anything and everything that you would need to help you. Plan it out.
4. Learn - Sometimes when you're on your own, you learn new things that inspire your independence. Be open to new experiences.
5. As long as you can eat, drink, use the bathroom and be warm - you'll be ok. One day will not pull you down.
My daughter loved random days of no attendant. She and I would cuddle in bed while watching television. We'd eat whatever we could manage (usually snacks,) and do lots of creative things to keep occupied. I was extremely lucky that she listened to me and trusted me. It made my life easier. Plus she's very independent.