***So don’t run as administrator. This is not good.***
So what do you do if you’re an only user and have to be administrator?
You don't have to be the administrator even if you are the only user. Go into system preferences, select Accounts, create a new administrator user (give it an imaginary, difficult but memorable name such as "Senat0rF0gh0rnLegh0rn" [those are zeros where the 'Os' are, just don't use "Admin"!], and a hardened password that you won't forget), make that account an administrator. Turn on Fast User Switching in Login Options (that's at the bottom of the user list)... with the Name option selected. I'd turn off Automatic login. Now Log Off your account. Log into the new Administrator. Change your usual account to Standard User. Lock the Accounts Pane by clicking on the padlock in the lower left corner. Log Off the new Administrator account...
Log back into your usual account and continue your usual operations. You can still add software and install stuff, but you will have to provide the new Administrator name and password when you need to do that... a much safer way of operating. You can always switch to the Administrator for long jobs requiring administration by clicking on your name on the upper right of the menu bar and selecting the Admin account... and logging on. Always remember to log off the Admin account when not using it.