You may add a security lock to Jarme App in order to protect your private memories. However, forgetting the 4 digit passcode isn’t unimaginable. If you forget the passcode there is NO WAY to reset it.
But there is always a way around everything. If you uninstall the app and reinstall is back again then the passcode of your app will disappear. And since you will have to log back in again using your Jarme App email and password, there is no security breach either. Once you log into Jarme you can set another passcode again to keep your memories secure. But this time one that you will remember ;)