Two part answer.
To hide a personal file: right click on the file check the hidden attribute,
apply. The file is now hidden.
As far as security is concerned that doesn't do squat however as you can set
explorer to show hidden files (they are shown dimmed).
To be the only one to reopen it.
Do not share the file, do not give out your password. Do not have any other
administrator account on your machine.
Any file in the users documents folder will NOT be shared unless the user
did something specific to do the sharing. (if the file is being shared there
will be a pair of people added to the icon in lower left).
If you have ultimate or business you can also encrypt the file, this will
protect the file even from other administrators.
Do not leave your machine unattended while you are logged on, lock the
machine when you step away.
Michael