Usher canceled his concert hours before it was set to begin Wednesday, saying that he had to put his own best interests first. The famous singer posted the last-minute cancellation notice of his “Past Present Future” tour opener in his hometown of Atlanta on Instagram. He didn’t provide much detail as to what forced this. “For my 30-plus year career, 100% of my blood, sweat and tears has gone into putting on the best performance and creating a memorable experience for my fans,” Usher wrote. “I have every intention of doing that for this tour as well which is why I have to postpone tonight’s sh…