It's an adult approach to work. Like linkedin / Reid Hoffman's approach to career development: stop pretending you're joining a company for life; instead, treat employment as a tour of duty with limited duration. The company gets X from you, and you get Y from the company. At the end, you may or may not choose to re-up, with new goals for both sides.
ala https://hbr.org/2013/06/tours-of-duty-the-new-employer-emplo...
I explained that if it didn't work out, there was no sense for either of us in me staying on when it wasn't a good match. We then had a reasonable, adult conversation about hiring and firing and our approaches thereto.
It was honestly part of what sold me on the place. I think that companies that treat firing as some sort of spooky bogeyman are not so good at management. It's not like failing to talk about it means that firing isn't a possible outcome; it just means that people dance around it.