MONTREAL — The Montreal Canadiens are in the midst of a rebuild, and as sick as their players and probably their fans are of hearing of that, they wouldn’t hear it nearly as much if the team did not continuously provide reminders.This is the fourth year of it. The Buffalo Sabres, the Canadiens’ opponents in this second-round series that’s headed to a Game 7 on Monday after an 8-3 Montreal loss in Game 6, are completing at least the 13th year of theirs.Performing under playoff conditions takes time. It takes experience. It often takes failure.The Canadiens had a chance to go up 2-0 on the road in their first-round series against the Tampa Bay Lightning, and failed. They had a chance to go up 3-1 on the Lightning at home, and failed. They had a chance to eliminate the Lightning in Game 6 at home, and failed. They had a chance to go up 3-1 on the Sabres at home, and failed.And, finally, they had a chance to eliminate the Sabres at home Saturday night, and failed in spectacular fashion, turning a 3-1 first-period lead into a five-goal loss.The Canadiens could have become the youngest team to reach the conference finals in 33 years, when another team that began the playoffs with a lineup that also averaged 25.8 years of age not only reached the conference finals, but also won the Stanley Cup. That was the 1993 Canadiens, the last Stanley Cup winner in franchise history.With youth comes immaturity, and with immaturity comes learning opportunities.“I don’t know if maturity is what made us play like that. I don’t think that’s it,” said Canadiens coach Martin St. Louis, who then went on to explain how immaturity played a role in why his team played like that. “For one, you have to give credit to the other side; they played a very good game. We didn’t have a lot of calm, a lot of poise. You have to live these moments to learn. They’re stressful moments for players who want that result. It’s loud, it’s a lot of chaos.“Tonight, we weren’t able to see clearly through that chaos. We’re better than that.”