Manager David Martindale felt Livingston were undone by set-piece sloppiness after suffering his first defeat in management.
St Johnstone emerged as 2-1 winners at the Tony Macaroni Arena on Saturday, with a fine Scott Tanser free-kick and Shaun Rooney's towering second-half header doing the damage.
Rooney was afforded unforgivable space to convert Liam Craig's pin-point free-kick and it was far from the only time that St Johnstone looked more aggressive inside both boxes as they ended Livi's 14-match unbeaten run.
Martindale said: "I'm disappointed in the manner we lost goals. They defended their box a lot better than us — and I thought their use of set-pieces in attack was better than ours. They were more aggressive.
"We were very wasteful from those situations.
"The second goal is poor (to concede) and we miss big Jon (Guthrie) in both boxes.
"But it's credit to St Johnstone, who maximised their chances.
"We basically lost the game through two set-plays."
St Johnstone boss Callum Davidson, who endured a nervous finale when Scott Pittman halved arrears with a fine glancing header, hailed his two goalscorers — even if he did not initially realise Tanser's effort had found the net.
He smiled: "At Scott's goal, I actually thought it had hit the metal behind the goal and gone wide. It was only when I heard the shouts of 'yes' I realised he'd scored!
"And it was great for Shaun to get a goal. He's been patient and he's very good in both boxes. It was a fantastic header for his goal and that's the kind of threat he brings for us."
Davidson also revealed that midfielder Murray Davidson is "50-50" for the upcoming Betfred Cup final.
These sides will meet again at Hampden on February 28 but Davidson remains a doubt after he was on the end of a hefty challenge from Rangers attacker Kemar Roofe last Wednesday.
The McDiarmid Park boss said: "Murray is a quick healer so hopefully he will be back in time for it — he's 50-50 for the final."
