The 45-year-old brought the Dockers together in the middle of the MCG as joyous Brisbane Lions players celebrated around them.
"Don't be too hard on yourself, don't beat yourself up too much," Longmuir said.
"We play an imperfect game that is full of mistakes ... across the journey of their football careers, they would've made plenty of mistakes.
"It feels a little bit bigger right now because of what was on the line, but don't be too hard on yourselves.
"If we had've won we would've won together, but we lost and we lose together, so have each other's back."
Longmuir said there was no sugar-coating Fremantle's devastation after the seven-point defeat brought an end to their latest bid for a maiden premiership.
The Dockers had one hand on the cup when they led by 17 points in time-on of the final quarter, but conceded four late goals to lose in a horror finish.
"I've never felt so disappointed but there's a massive sense of pride in the group," Longmuir said.
"We came to play, we executed the plan, created so many opportunities for ourselves and competed our backsides off all day.
"But just didn't quite play out that 120 minutes.
"Clearly we're playing one of the best teams of all-time ... and they just found something and we didn't have an answer for their run-on late."
Longmuir said Fremantle's "journey is not finished" as they chase a long-awaited premiership and sustained success.
"We want to make sure we emulate something like (what Brisbane have done) and keep contending and keep putting ourself up there, year in and year out," Longmuir said.
"It's something we haven't done as a football club, but with the way we've built the list and the culture, that's what we set out to do.
"There's no guarantees and everyone starts at zero again next year, but I feel like we've got the capabilities in terms of character and talent."
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