Harrison delivered a huge showing as he skippered his side to a sensational 43-39 comeback success at Rodney Parade.
Saints were 22-3, 32-17 and 39-24 down against the Dragons but came roaring back late on and sealed the victory thanks to Tom Collins' eye-catching breakaway try.
It means Saints will now look forward to a Challenge Cup quarter-final at Franklin's Gardens on Saturday.
And Harrison said: "It's pretty much the story of our season: we have a poor first half and then we decide to start turning up and defending well and putting our game on the pitch in the second half.
"But I'm massively proud of this team - f***, we don't give up, and you can't teach that.
"You can teach all the skills and all the pretty stuff, but you can't teach heart.
"I'm really proud to be a part of this team."
And he added: "To go down to 13 men, it's a hard place to be, it's tough to get your head around the disadvantage that you're at.
"We had a plan if we went down to 14 but we went down to 13 so the plan sort of changed a little bit more, but the boys stuck to it.
"It really showed the character of this team.
"We're inexperienced but you can't write this team off.
"The 15 players we're missing is a big chunk of our team so for these young guys to step up, it's just the DNA we're instilling in this squad.
"Massive credit to the boys."