The Boston Celtics season will either move forward with a quick turnaround to face the New York Knicks , or it will come crashing to an end. Game 7s can be weird, with desperation leading to unique lineups, wild decisions, and players who rise to the occasion or wilt under the extreme pressure.  Here are seven thoughts heading into Game 7 against the Philadelphia 76ers .  ► This is where the “they’ve been here before” thing is supposed to take hold. We can, for a moment, forget the failures of Game 5 and Game 6 and focus on the fact that this Celtics roster has champions on it. Recent champions. Tatum and Brown have won before. They have come through in the biggest moments.  Tyrese Maxey has not. Joel Embiid certainly has not .  This is where the analysis goes out the window. Anything is on the table if the game starts to get away from a team. Every player is available. Every trick is on the table.…