By Albert Breer There’s a saying Panthers owner David Tepper uses with his football people that those staffers have been told comes straight from the world of high finance. Don’t let one mistake become two. It is that mantra that might best connect how he runs a hedge fund with how he’s run his football team—and it can go a long way in explaining both what happened Monday morning in Charlotte and the challenge he’s still facing through a labored, painful adjustment to running an NFL franchise. Frank Reich is gone now. The writing had been on the wall over the last couple of weeks, as Tepper’s …