How to deal with the fragility of the Internet?

About three days ago, as I was sending out an email newsletter, and changing some theme settings, my website went down. The dreaded 500 internal server error. White screen of death, for about three days.

Having my website in operable for about three days was a nightmare. Why? First of all, I realized; about 10 years of work and effort, going up in vapor, and being inaccessible.

Then the thought; is it possible to create some sort of anti-fragile, or at least robust website? Something that *cannot* go down?