Version control systems like git (and svn) are also very helpful when working alone.
They allow you to track what you changed, when you changed it and why you changed it. It gives you a history of you changes and allows you to restore any older version of your files.
For example you can use it for config files. Instead of making a lot of backup files it is much easier to store the older versions in you version control. If things break immediately you have an easy undo. If things break later you have a history of your changes and you can identify the bad change.
Especially git also allows you to write better code by letting you concentrate on the actual changes you do. - Think of building you code as a sequence of functional changes, which is much more understandable than only the final code.