We have done a lot of work on this project. And according to Murphy's, Sod's, or Finagle's law, something bad is bound to happen at the worst possible moment. Computer crashes, corrupt files, lost data, and the like are inevitable in our computer-centric life. We can't avoid these things happening, but we can take precautions to mitigate the damage. The first step is to save often, while the second is to back up our work.
There are three primary types of backups we can create. Although the methods are generally related to your level of experience, we should always look for the method that is best for a given situation.