The Gunners lost at home for the first time in 2015 as Bafetimbi Gomis stepped off the bench to score the only goal of the game.
Arsene Wenger says Arsenal will "take encouragement" from their home defeat to Swansea.
The Gunners saw their unbeaten home record in 2015 come to an end as Bafetimbi Gomis stepped off the bench to head home the winner.
It came after the home side dominated possession but couldn't find a way past Lukasz Fabianski, who was inspired on his return to north London.
And after the game, Wenger insisted his side did more than enough to claim the victory.
"We were a bit unlucky with the goal," he told Sky Sports.
"There are a lot of positives. This kind of game you play 20 times and win 19 times.
"In patches our domination was top quality. You have to learn from defeat and we take encouragement from a defeat like that.
"Swansea deserve credit for their defensive display but they probably had the fewest passes in our half of any team here this season."