long time ago people use personal dairies to writer there personal things,
but now days people are getting advance and now they use laptop and desktop computer instead of diaries.
and they use MS Word files to save their personal data, even some personal talks are there, so you must keep them safe by protecting them with password
because if anybody use your computer its not personal computer anymore,
to encrypt your ms word file go to info option and then go to protect document after that click on encrypt with password and put your password and click ok
now your file is password protected and no one can access without your password.