Saturday's 1-0 win over Chester means the Cobblers are guaranteed a top-three finish in League Two.
And Calderwood was relieved to secure automatic promotion - after suffering play-off heartbreak in the last two seasons.
He said: "I've had two miserable summers, losing in the play-offs, so I am not just going to celebrate, I am going to celebrate all summer.
"I came from the basement to the top playing football. And I am doing the same thing in management, but I've enjoyed this moment as much as any in my football career.
"The play-off defeats were disappointing. Last season we were close but not quite good enough but there was an injustice in our semi-final defeat the season before at Mansfield."