Don’t hesitate to cancel an operation if you change your mind. Remember that you can often press “Cancel” buttons, “Back” buttons, the <esc> key, close the window, or similar action to back out of layers of configuration without permanently changing your settings.
Canceling can be particularly helpful when navigating complex configuration menus when you are concerned that you may have changed a setting that you do not wish to save.
Similarly, if you spell-check your email automatically on sending, you can can send an email, catch a spelling mistake, and then cancel the spell-check and make another change to the message if needed before resending.