There were was jubilation for the 40,000-strong Red Army at Parkhead in March after the Pittodrie side picked up their first of silverware in 19 years by beating Inverness in the Scottish League Cup final.
Victory over their Scottish Premiership rivals will see Derek McInnes's side return to the east end of Glasgow for the May 17 final and Langfield insists Aberdeen, second in the table, could not be more confident going into their second semi-final of the campaign.
"Hopefully we can go out again and give a good account of ourselves and get back to Parkhead in May," said Langfield. "It was an amazing occasion and for us to do that again for the fans would be an incredible achievement.
"We know it is going to be a very difficult game against a very good side. But we have a squad now who believe we can win every game."
Aberdeen beat Tommy Wright's side 4-0 in the Scottish League Cup semi-final at Tynecastle at the end of January and have won two and drawn one of their league meetings.
However, Langfield will not read anything into that record.
"St Johnstone are a very good side. I do not believe they get the credit they deserve," he said.
"For a number of years now they have been in the top six and this is their second semi-final this season.
"They have some players who can change games, for example Steven MacLean, who I rate very highly, and of course who we had here.
"They also have Stevie May who is scoring goals. The two of them link up very well together. So we are under no illusions how difficult it is going to be."
He added: "If things don't go right it won't be because of a lack of effort. As a team and a squad we will give it our all. We are very determined to win this game."