Steve Elliott's goal late in the first half dented the Cobblers' automatic promotion hopes and Boothroyd admitted it was the type of match they needed to win if they were going to hold onto a top three spot until the end of the season.
"I thought we were very nervous to start off and it could have gone either way in the first half," he said.
"But you've got to be strong and you've got to be resilient. If you want automatic promotion then you've got to win games like this.
"We've got to be cool enough in the head to be competitive in any game and you've got to have the fire in the belly.
"I thought in the first half we didn't function as well as a team, but in the second half we looked much better."
Boothroyd was not pleased with some of the decisions that went against his team.
"What is disappointing is when an official is not quite sure if it's a corner or not, and then before the ball even comes in, he's blowing up for a free-kick against," he said.
"I won't make excuses and you've got to give respect to your opponents, but every single week we've got to get Adebayo (Akinfenwa) a new shirt because they get ripped and pulled."