Go to the Members Feature, find yourself, hover over your icon and choose the Delete Button.
This will prompt a window asking whether you are sure you want to leave the project:
To delete yourself, press "OK".
Note: If the Admin has changed add/remove permissions, you may be unable to remove yourself from a Project. Admin permissions settings are only available in premium Independent Projects and premium Team Projects. To see all of the benefits of upgrading your Independent Project of Team to Premium, click here.