Day One is really very handy app for anyone interested in writing daily journals. It syncs beautifully to all your devices using either Dropbox or iCloud. You can use a password to protect your journal from prying eyes and it works perfectly. However, if you forget the password, reseting the password is not easy. You have to go through a number of steps, depending on whether you are keeping your content synced through Dropbox or iCloud. The detailed procedure is given here. But, the procedure given at the official support webpage does not apply for those users who are using iCloud for syncing on Mountain Lion. The reason, there is no ‘Mobile Document’ folder that you can access on Mountain Lion. But you can do it by deleting the ‘security.plist’.
‘Go to System Preferences’ -> ‘iCloud’
Click on Manage and Choose ‘Day One’ and then find ‘security.plist’ and delete it.