BOSTON -- In the wake of their season-ending loss to the Golden State Warriors on Thursday night in Game 6 of the NBA Finals at TD Garden, the message from the Boston Celtics was that the future is bright, and that this loss was, in their eyes, just the beginning.

"It's definitely is tough," Marcus Smart said of Boston's 103-90 loss to Golden State. "But it's definitely one of those things we've been through hell to get here, and you take that. You know what I'm saying? We got to use that.

"It's going to be tough. That's what I know for myself. I'm viewing it and looking at all the s--- we had to get through to get here just to even get to this situation to have an opportunity."

The Celtics, who had won their first three elimination games in these playoffs to get to this point, were unable to make that happen a fourth time Thursday, as their series-long issues offensively once again reared their head.

For all of the attention paid to Finals MVP Stephen Curry, Boston held the Warriors in and around the low 100s in scoring in each game of this series. But, as Jayson Tatum said, it was Boston's poise on the offensive end that repeatedly failed the Celtics, as they committed one turnover after another.

The Celtics had another 22 turnovers in Game 6, while Tatum -- who finished with an NBA-record 100 giveaways in this postseason, the most ever by a player in a single playoffs -- had five of them alone.

In the game's opening minutes, it looked like Boston would be in business. The Celtics came out flying at both ends, running crisp offense and harassing the Warriors defensively. That allowed Boston to jump out to a 14-2 lead four minutes in, sending the TD Garden crowd into a frenzy and advancing the possibility this series could be headed back to San Francisco.

But then the Warriors responded. And responded. And responded. Minutes ticked by, and Golden State kept scoring. Boston kept turning the ball over. By the end of the first quarter, the Warriors had taken the lead -- one Golden State would never give back. That advantage ballooned to 15 at halftime, and while the Celtics fought valiantly in the second half, they never truly threatened to come back.

"This is tough, getting to this point and not accomplishing what we wanted to," said Tatum, who hardly spoke above a whisper during his stint at the podium after his latest rough game in this series, finishing with 13 points on 6-for-18 shooting in 40 minutes. "It hurts. You know, we all could have done things better. I feel like I could have done a lot of things better. But, you know, like we said, we competed, we tried all season, all playoffs."

Trying, though, wasn't enough to solve the puzzles Golden State presented this Boston team. The Celtics were able to overcome the problems they gave themselves from a turnover and execution standpoint against the Milwaukee Bucks in the Eastern Conference semifinals and the Miami Heat in the Eastern Conference finals.

The Warriors, however, were a different story, as Curry and Golden State's experienced roster threw one look after another at Boston throughout this series, and the Celtics -- Tatum in particular -- struggled to adjust.

And, as Boston begins a long offseason of wondering what might have been -- particularly after rough collapses in the fourth quarters of winnable games in both Games 4 and 5, and after finishing the postseason with a dismal 6-6 record at TD Garden -- Celtics coach Ime Udoka, who was on the San Antonio Spurs' coaching staff when they lost to the Miami Heat in seven games in 2013, said this loss will linger for some time.

"It's going to hurt. It will hurt for a while. Probably that stuff never goes away. I've lost one before.

"That was part of the message. Let it propel us forward, the experience. Growth and progress that we made this season. Obviously, getting to your ultimate goal and fall a few games short is going to hurt. There are a lot of guys in there [that are] very emotional right now."

One of them was clearly Tatum, who looked like he didn't want to speak for most of his postgame news conference. But another was big man Robert Williams III, who bounced back from the knee pain that has dogged him for most of the playoffs to be Boston's most impactful player in this series.

"It don't stop hurting," he said, when asked when he will begin moving on from this loss. "Honestly, it never stops hurting until we're back in this position again. Starting with the beginning of the season.

"Just got to be better, man. Got to be better. Everyone got to take a step up, add a little intensity to everything we're doing. But it never stops hurting."

Still, much of what the Celtics said after this one is that the future is quite bright in Boston. All eight of the team's top rotation players are under contract for next season, and of them only Al Horford is older than 27.

After a slow start to the year that saw Boston sitting at 23-24 in late January, the Celtics completely flipped the script, going 28-7 to end the year, and then going through superstars Kevin Durant, Giannis Antetokounmpo and Jimmy Butler -- the latter two in seven-game series -- to make it this far.

Ultimately, though, the combination of Curry and the veteran moxie and experience on this stage for the Warriors was too much for Boston to overcome. Now, the Celtics will head into the summer thinking about what might have been and excited about where this franchise is headed after making it to the NBA Finals for the first time in 12 years.

"The future is bright," Jaylen Brown said. "I always look at adversity as opportunities to shape an individual. For whatever reason, it wasn't our time. That means we still got a lot to learn. Personally, I still got a lot to learn.

"For me, it's always about growth. Continuing to get better, continuing to find different ways to lead. That's what it's about. The future is bright. I'm excited to get back next year."