In ancient times, well ok the 1990’s, if an application failed it meant the whole Mac failed. You really did have the thrown the baby out with the bath water.
But for a long time now you won’t lose the data in your unsaved* Excel spreadsheet if Word fails for some reason.
If an application stops working for one reason or another here are the top two ways to send it to oblivion.
First, try pressing the Option key on your keyboard and then clicking -and holding – on the icon in the dock. This will produce an applications menu and from there you can choose Force Quit.
The second is to click on the Apple menu, choose Force Quit and then select the misbehaving application (usually in red with the words “Not Responding” alongside). Once selected, choose Force Quit.
* On the subject of something being unsaved… a trick I learned many many years ago was to save every few minutes regardless of what it was I was doing. This was especially true when using Word, Excel back in the day. I will be the first to admit that today this is less and less important because applications have all kinds of built in auto save functions but its better to be safe than, well you know the rest.
To that end I always have my left hand moving over the keyboard and every minute or so I quickly press Command S and then move on. Its almost instinctive now and, I think, a good habit to get into.