The Links Park men looked to be on their way to a play-off final against Queen’s Park at 2-0 up in the game, only for Airdrie to spark a fightback and edge past the Angus side 6-4 after extra-time and 6-5 on aggregate.
It was yet more play-off misery for Montrose but boss Petrie is confident his squad has the mentality to pick themselves up and go again when the new season begins.
He said: "If we keep putting ourselves into a position in the play-offs, then eventually we’ll get our break or do well enough to go and win over two legs.
"The boys are gutted, of course they are.
"We’ll have a day out with them now, a couple of them won’t be here next year and the loan players will go back to their clubs and we hope they do well.
"We’ll regroup because we have a great group of boys who have just fallen short and there’s nothing to be ashamed of in that.”
There was no disguising the shock within the Mo ranks post-match as they tried to come to terms with the defeat.
A large travelling band of fans had roared the side on, only to be silenced by the home side.
Despite the loss, Petrie was proud of the effort of his players, not only over the two-legged tie, but across the entire League One season.
"We’ve had a great season and gave a really good side, who haven’t lost a game in 20, a right good battle,” he said.
Mo arrived in Airdrie with a goal advantage from the first leg, which they added to in the game.
At one point they were 3-0 up on aggregate and Petrie admitted he was frustrated not to see the game out.
“We gave ourselves a great chance to get to the final and put ourselves into a position, but then lose goals, soft goals from our point of view,” he added.
“Then we score a third goal through Lewis Milne and think ‘just go and defend for five or 10 minutes’ but then concede again straight away.
"Credit to Airdrie, we knew they’d throw everything at us in the second half, which they did.”