Is your web site up? How do you know? There are monitoring tools you can use to find out. You can see how long it is down and how long it took to get it back up. The Internet is a tough place; things don't always go as planned, but it is always changing and you can always fix it. When your site is down is it because you can't see it or is it down in the world? Sites like http://www.site24x7.com can see if your site is up around the world. It is possible that your site is not working where you are and is working the rest of the world. There are great ways to mitigate that. One is to use a CDN (content delivery network), they put your site on their servers around the world. That way if something happens to your server the site will be up on all the other servers so no one will know. One of the side benefits is that the site is closer to your users and it loads faster and the load on your server is less, so you can handle more traffic. CDN's are getting cheaper and more relible, check it out. Any issue can be fixed. Relax.
Have a great and peaceful day.