This is who the Miami Heat have become. Living on the edge. Seemingly every night. A night after coming up short following a rally from 22 down at home against the Milwaukee Bucks, Erik Spoelstra’s team this time coughed up a 20-point third-quarter lead to again find itself in yet another game decided at the wire. This time, survival. Barely. And, so, a 98-94 victory Wednesday night over the Charlotte Hornets at Spectrum Center, an 8-8 record at Thanksgiving, and an exhale, thanks, in part, to the late contributions of guard Tyler Herro. “From the mental toughness standpoint, we’re getting pretty comfortable in these kinds of games,” Spoelstra said.