Jayson Tatum was left with a "terrible feeling" after the NBA Finals series defeat as he called on the Boston Celtics to "take it up another level".

The Celtics struggled against Stephen Curry in Game 6, the Golden State Warriors winning 103-90 after he posted 34 points, hitting six-of-11 threes, while adding seven rebounds and seven assists.

That helped the Warriors to an unassailable 4-2 series lead and fourth NBA Championship in just eight years, while Curry claimed his first NBA Finals MVP award.

Golden State were 2-1 down in the series at one point, but a three-game winning run meant Boston's 14-year wait to win the NBA Championships continued.

Tatum expressed his frustrations after the match as he admitted the Celtics fell short of expectations.

"It's hard. It's hard getting to this point. It's even harder getting over it, the hump, and win it. It's been a long journey, a long process," the Boston star said.

"Being with this group, the things we've overcome throughout the season, getting to this point. Just knowing how bad we wanted it, coming up short. It's a terrible feeling.

"That's what I took from it: it's tough. You got to take it up another level to do what we want to do.

"We all could have done things better. I feel like I could have done a lot of things better. But, like we said, we competed, we tried all season, all playoffs."

Marcus Smart was speaking alongside Tatum and vowed that the Celtics will bounce back stronger after the experience of the Golden State defeat.

"For us, it's just hard-nosed, it's who we are," Smart added. "We're a family. We take and accept every challenge head on no matter the outcome, no matter the advantages we have or disadvantages.

"We're going to take it full-heartedly. The guys came out here and competed. We could have [given] up, but we didn't. I think that shows the foundation that we have here.

"We see what we're capable of. We got a taste of it. We want the whole thing. I know for a fact that we're going to be back a different team. We're going to put in the work. But this one's going to hurt."