The Boston Celtics readily admit that the aftermath of their championship celebration has impacted their intensity this season. “We were a lion last season, and some games this year we’ve looked like a house cat,” center Kristaps Porzingis said after the Celtics’ 122-107 win Saturday over the Dallas Mavericks. “We want to have that spirit as a team this year, and it’s tough. Obviously we can’t trick ourselves and make it [like] it’s playoffs every game. It’s tough, just human nature. But we know the group that we have and we know that we’re going to bring it to the big games, but we need to bring it consistently and keep building on top of good wins like tonight.”