The Belgian came off the bench to score and set up Oscar Bobb's stoppage-time winner in his first Premier League appearance since suffering a hamstring tear on the opening day of the season.
"I'm dead honestly, it was crazy," De Bruyne told TNT Sports. "I missed this. I had a big injury and I needed the time.
"It was more willpower than anything else but it was crazy.
"I know I'm not able to do that for 90 minutes at the moment, but I can put in a shift for 20-25 mins.
"I feel it in my lungs with the cold, but it can't be any better than this."
A sixth consecutive win in all competitions moved City up to second in the Premier League table and within two points of leaders Liverpool.
Pep Guardiola celebrated wildly at full-time as City now head into a two-week winter break in high spirits.
And on their return, De Bruyne could be joined by Erling Haaland, who has missed the last nine games due to a foot injury.
"To come here is always a difficult ground. Everybody was happy for me with everything that happened this year," added De Bruyne on the celebrations.
"We want to try and compete again for the league and before the break, to win here at St James' Park, against a tough Newcastle, is a big win."
