Shaun Wane's men came back from 14 points down in the second half to become the first team since St Helens in 2006 to do the double.
"We can't be decisive about whether or not that was disruptive, you have to be able to handle those situations," he told Sky Sports News. "We weren't able to, and in the second half field position hurt us more than anything.
"Also our discipline was an issue, big time. We got smashed in field position, in penalties - it was seven two against us in the second half. Wigan are fantastic close to the line.
"Wigan were way too good tonight and deserved it. It's a really big effort for them to do the double."
The Cherry & Whites defeated Hull FC 16-0 in the Challenge Cup final in August.