As you’re working on a project, it’s convenient to simply hit the “save” command on your DAW or other software/hardware to store the current state of your project. But this overwrites any older versions that have been saved under the same name.
In order to be able to “go back in time” to earlier versions of the project, use the “save as” command instead to store the project under a new name. This creates a new file for the project, and preserves the older versions of the file.
We use a file naming scheme like this to keep track of the project over time: My Song.01, MySong.02, MySong.03, and so on.