Neil Lennon vows to make Thursday's appearance in front of the Scottish Football Association's judicial panel his last.
The Celtic boss completed a two-match touchline ban - for criticising referee Willie Collum following the Hoops' Scottish Communities League Cup final defeat by Kilmarnock at Hampden in March against Rangers - at the weekend.
On Thursday, he was back at Hampden where he was handed an immediate three-match touchline ban today for confronting referee Euan Norris after his club's William Hill Scottish Cup semi-final defeat by Hearts last month.
He received a six-match ban in total but half of the punishment is suspended until the end of next season, and that, according to the Northern Irishman, is enough for him to learn his lesson.
Following Celtic's 1-0 Clydesdale Bank Premier League win over St Johnstone at Parkhead, courtesy of a first-half goal from Anthony Stokes, Lennon said: "The judicial panel don't want to be punishing people but when you cross the line...I expected to be punished and I have been and I am going to learn from this.
"All I will say is that I got a fair hearing, I think the punishment is pretty fair as well.
"I have apologised to the referee in correspondence and he has responded and he is grateful of that and we move on.
"I will have a suspension hanging over my head (next season) and that is a warning for me.
"If I step out of line again I could get three matches-plus and I don't want that."
Lennon made seven changes to his side in order to give some of his fringe players a game and although it was far from a vintage performance, the champions did enough to win.
He said: "I was very pleased. It was another clean sheet, 24, that's a record, and it takes us to 90 points with two games to go and that's tremendous consistency."
Celtic's stand-in keeper Lukasz Zaluska made a good save from Murray Davidson just before the break but aside from that, the visitors rarely threatened.
St Johnstone boss Steve Lomas was left ruing Davidson's miss just but he was also unhappy about Celtic's goal.
He said: "I thought we had a great chance just before half-time which could have gone in and I am little bit disappointed with the manner of the goal.
"I didn't think it was a corner at the start and we were told that it was offside.
"I could be proved wrong but when the cross came in, Bangura helped it on and the guy (Stokes) was offside.
"I thought the referee was very good, he let things go, but it is just disappointing again that my boys put so much in and we are talking about key decisions again."