I was thinking about this exact topic yesterday. I thought about it a little more introspectively too. I was hired and within my probation period, fired from a position because I "was no longer a good fit". What didn't make me a good fit? Was it my attitude or my commitment? Was it just like mixing oil and water? Why would they hire me in the first place? How was I different from the interviews to the point where they made the decision to let me go? I kind of let my brain do its thing and run through a hundred scenarios, I didn't try to stop my thought process as I normally would. I came to the conclusion along the lines of the Donny Brasco story, after a certain amount of time they just discovered that the company didn't hire the person they thought they did.
I took it all in and am very much more aware of myself and how I present myself to my customers, as a business owner. I am never going to be perfect to everyone but I am for sure aware now.
Now as I am thinking about hiring employees, I would say that no one is the an absolute perfect fit, but your job as a leader is to find the least worst fit!