The Gulls extended their winless run to a third game as Dons substitute Rashid Yussuff and George Moncur scored in the final 11 minutes, ensuring Ling's men stay fourth, one point behind the automatic promotion places.
Third-placed Crawley only managed a draw at Dagenham, meaning the Gulls can still achieve automatic promotion, but Ling conceded defeat to Stevenage at Old Trafford last year is playing heavily on their minds.
"As a group of players we didn't perform to the standards that we've set all season and that's why we've lost the game," he said. "Nerves are creeping in, you try to take it out of there, try to take it on your own shoulders and take it off the players.
"But they know the outcome and I think with losing the play-off final last year, they are doubly nervous in my dressing room at the moment.
"You can view the automatic promotion race in two ways, you can view it as we're still in it, or you view it as a missed opportunity, but as I've always been a positive person I'll view it as we're still in it."