Altering the default template is fine, but in some cases you might want to alter the template without changing the default version. You can do that easily with Wright.
This is the most common thing people do, and we have designed Wright to be able to edit freely while keeping the core intact. If you look at the template directory, you will see template.php. This is the file that is loaded and handles the HTML output. Rather than making changes directly in this file, you can copy it and rename it to custom.php. If you include custom.php in your template directory, it will be used instead of template.php. This will prevent your changes from being overridden.
This video shows you how to safely customize the layout of your Wright template: