Over the past two months the Bruins have done an unbelievable job of, as a former goaltender of some renown might have put it, proving people wrong. The Bruins silenced the doubters who talked about their rather mediocre regular season and didn’t believe they’d be able to “flip the switch” and be ready to play well when the playoffs came along. Well, as a team that is now within two wins of the Stanley Cup, the B’s have proven that, yes, a veteran team that knows how to win actually can rediscover its game in the postseason. The B’s did it again, big-time, in an inspiring Game 7 comeback against Toronto in the first round — scoring two goals in a stunning final 82 seconds of regulation that saved the season and, probably, lots of jobs. It happened again when injuries forced the Bruins to play three rookie defensemen for several games. That’s supposed to be a formula for disaster. But the B’s, yet again, made it work — with little-known (and little) Torey Krug becoming an overnight sensation. Again and again since May 1, the Bruins have reminded us why we love sports so much. Because you just never know what’s going to happen, regardless of how bleak things might appear. “When our backs are against the wall, we show up,” Nathan Horton said yesterday. “We play for the guy next to you and we all know what we have to do now. We can’t lose and we’ve got to come to play.” Now the Bruins face their greatest challenge: finding a way to beat the Chicago Blackhawks tonight in Game 6 of the Stanley Cup finals at the Garden and force a Game 7 back in the Windy City.