The American held a five-shot lead with just four holes remaining on the final day in Atlanta.
Despite spurning a commanding position, 34-year-old Dufner is determined to take some positives from the competition.
"I knew what was a stake. I was confident with my game, but just didn't quite execute a couple of shots coming in," said Dufner.
"I'm disappointed now, but there's a lot of good things to take from this week.
"I love the competition and I want to be as good as I can be. If that's 20th in world with no majors, first in the world with ten majors or never win a Tour event I'll be fine with that.
"I'm not going to let this define my career. I have a lot of things ahead of me."
Dufner's second place finish has seen him rise to 38 in the world rankings.