If you really want to sleep easy, the ultimate backup solution includes backups for your backups.
The first steps in getting properly backed up are the big ones. Getting a real backup in place, making it happen automatically and making sure it works. All the keys to a happy and successful backup recipe.
Once you're well in order, there's one more step you can take to really rest easy and that's setting up additional redundancy — basically a backup for your backup!
I have a personal example — my family photo archives. I never want to feel the pain of losing my digital memories, so I run multiple backups.
I have a local archive on my main computer, which is automatically backed up to network-attached storage in my home. That backup is then further backed up to the cloud using a tool called Jungle Disk, which sends it all to Amazon S3. I also have a live accessible online backup that lives at SmugMug, which lets me share photos with friends online while also acting as a full backup of my local archives. And I've even got the extra security that SmugMug runs its own backups.
Overall, that's a count of four full backups of my photos — not including my main archive (because remember, an archive is not a backup).
Once you have that kind of redundant backup in place and know your digital life is incredibly safe from loss, you'll sleep better than you ever have before.