BOSTON — Miles McBride was confident in the morning, steadfast that he was happy with the looks he was getting and that he had to keep shooting.

By nighttime, he proved himself right.

McBride’s best performance of the postseason came in the Knicks’ 108-105 overtime victory against the Celtics in Game 1 on Monday night at TD Garden.

He finished with 11 points — his most of the postseason — on 4-for-8 shooting from the field and 3-for-6 from 3-point range along with two rebounds, an assist and a steal.

“Honestly, I keep trusting myself,” McBride told The Post. “I’m shooting with confidence.”

In the first round against the Pistons, McBride averaged just 3.8 points per game on brutal 26.7 percent shooting from the field and 26.7 percent from deep.

The Celtics possess the best bench player in the league in Payton Pritchard, who won the league’s Sixth Man of the Year award.

McBride, the top Knicks bench player, matched up with Pritchard plenty on Monday and figures to going forward. Pritchard finished Game 1 with 13 points.

The Knicks will gladly take McBride nearly matching Pritchard’s output as they look to mitigate the large bench-scoring discrepancies they’ve endured throughout the playoffs — and the entire year.

“Obviously he’s a great player, he’s done great things this season and obviously, [they’re the] defending champs,” McBride said of Pritchard. “It’s a tough matchup for anybody, but we’re going to do it as a team. No matchup is individual. We’re going to do it together.”

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On the defensive end, McBride was subbed in for Brunson when the Celtics had a chance to tie the game, down three points, with three seconds left in overtime.

“Keeping it simple,” coach Tom Thibodeau said of McBride. “Not overthinking, not forcing things. Read the game, the game tells you what to do. Play to your strengths, cover up your weaknesses. When he does that, he’s terrific.”