Boston Celtics forward Jayson Tatum lives to play in the present but the recent past is never far from his thoughts.

That was the sentiment Tatum expressed in the wake of Thursday night’s 107-87 rolling of the Dallas Mavericks in Game 1 of the NBA Finals at the TD Garden. Tatum played 42 minutes and finished with 16 points, 11 rebounds and five assists.

“Just staying present, staying in the moment (and) like I said, I was, in a positive way,” said Tatum. “I was nervous before the game. I was like a kid first day of school.

“I know how exciting and big of a deal all of this is, so just finding a space to enjoy the moment and have fun playing basketball.”

Tatum was in the same position in the 2022 NBA Finals when the Celtics beat the Golden State Warriors 120-106 in Game 1 at the Chase Center in San Francisco. The Warriors’ deep experience in the finals took hold and they ran the table after trailing 2-1 to win their fourth title in nine years.

“Maybe last year, us losing in the conference finals,” said Tatum. “Maybe I just expected that after we lost in 2022 that it was guaranteed that we were just going to keep coming back, and this is like our time.

“Last year it was just kind of a wakeup call to not take anything for granted, because you never know how many opportunities that you might have.”

The “last year” Tatum referenced to was the Celtics’ elimination by the Miami Heat (4-3) in the 2023 Eastern Conference finals. The Heat jumped out to a 2-0 lead in the series and advanced to the NBA Finals with a 103-84 win in Game 7. The Celtics unrealized expectations in 2023 was the source of anxiety for Tatum before the opening tap against the Mavericks.

“It felt great,” said Tatum. “To be honest, I was nervous. I ain’t going to lie. I was nervous in like an anxious way, as like a little kid. It’s surreal being in The Finals. When you’re young, I guess, in your career, you think you’re always going to go back. Last year was kind of like a wake-up call when we didn’t make it.

“So, getting back to this point and being here is really a big deal. We played well tonight. There’s a lot of things we feel like we could do better. But it definitely does feel good to win the first game. But we know that two years ago we won the first game and the outcome of that series. So, we still have a lot of work to do.”

The Celtics look unbeatable when injured center Kristaps Porzingis entered the game with 7:17 to play in the first and took over on both sides of the court.

But a Mavericks’ 22-9 run that started in the second carried into the third. Dallas cut the lead to eight points, prompting Celtic coach Joe Mazzulla to call timeout. The Celtics broke from the huddle and went on a 14-0 run that sealed Game 1.

I think our offense got a little stagnant and it had a lot to do with our spacing,” said Tatum. “They kind of put us into some bad ways on offense which kind of threw off our spacing and slowed us down.

“They started to get stops, running in transition, but that’s part of it. They’re going to make shots. That’s a really good team over there. We just did a great job of responding in real time after Joe called that timeout. They cut it to eight, we came to the bench and talked about it, executed, and made plays and took the lead back up.”