We recommend that you keep your past projects in Archive, just in case you ever need to reference back to them. Archived projects don't count towards your plan limit, so it never hurts to keep them.
If you do need to delete a project, you'll first need to archive it. To archive a project, hover over the project you'd like to archive, then click on the gold Archive link that appears.
Next, access your Archive folder by clicking on the Archive tab towards the top of your project dashboard.
Once in archive, hover over the project you'd like to delete and click on the gold Delete option that appears to the right, and then reconfirm that you'd like to delete this project.
Please note, once you delete a project, you won't be able to bring it back, so please delete with caution!!