The mind is a terrible thing to use.

At least in games.

And one guy who wholeheartedly agrees is Knicks rookie Frank Ntilikina, who more and more is adhering to the advice of teammates and coaches and playing more on instinct rather than thinking everything through as if the NBA were advanced calculus. Jarrett Jack, veteran guard and mentor to the rookie, has seen the difference.

“He’s way more sure of himself and it’s showing in his play,” Jack said. “His game is maturing and right around this time, Christmas, the top of the year that’s when [rookie] guys start to get a handle on the task ahead of them and he’s done a tremendous job.”

Ntilikina has seen the difference, too. His growth is impressing all sides. In the Knicks’ 111-104 win over the Nets on Thursday at Barclays Center, Ntilikina again played the entire fourth quarter when he scored all seven of his points and passed for two of his eight assists. Ntilikina finished a plus-14, the best mark of any player in the game.

And a lot had to do with being instinctive.

“I understand what he [Jack] says,” said Ntilikina, who hit a 3-pointer at 3:09 that put the Knicks up six — and that came well after a steal and layup early in the fourth when the Knicks led by seven.

“He’s done that several times this year, hit big shots. He’s probably ‘sneaky quick.’ He knows angles. He made a great crossover and got to the middle of the free-throw line for an easy jump shot,” coach Jeff Hornacek said.

By just doing.

“Sometimes, I have a tendency to hesitate on my shot,” Ntilikina said. “Now I feel more comfortable while getting a lot of reps. Hitting shots in the real game gives me confidence.”

Yeah, those phony games rarely help.

“I just need to keep working, keep getting reps, keep taking those shots,” he said.

And keep avoiding all that thinking.