The stand-off was part of a big group of Warriors involved in Scotland's Autumn Test campaign - a period that saw Glasgow slip to fourth in the PRO12 after a 19-9 defeat to Scarlets last Friday.
Duncan told the Evening Times: "It's just exciting. I know we had a disappointing result on Friday but I'm excited to come back to a good atmosphere like the one we've built with Scotland.
"I'm glad to be back among the boys here. We've got a big couple of weeks ahead of us. I'm desperate to go forward and grasp every minute I can get at Glasgow.
"We have a huge run of games coming up and, with four at home, it will be the key to our league and European success. It's a great challenge and, as a player, you need to respond positively to the opportunities that come your way."
Glasgow face he Welshmen on Sunday before the European Rugby Champions Cup double header against Toulouse.
Duncan says that having so many Warriors being on Scotland duty has not hampered their training for the Guinness PRO12 meeting with Dragons.
Duncan said: "When you walk back through the door your mind is completely on Glasgow. Throughout the month away we were still popping in on our days off to see the boys, or even coming in for a stretch or a massage.
"It's all about driving Glasgow forward. We all understand that Friday wasn't good enough and we didn't meet our standards. We have to draw the line there and look forward and keep driving upwards.
"Regarding the game in France, it will be a real battle. But Glasgow has had good success over there in the past. I believe we have proven we have a squad good enough to compete at this level over the first two games, so it's all about showing it again."