I was 19 and playing for Celtic's reserves. I was left in no doubt just how much I had let down my team and myself.
Sean Fallon later told me that if I was going off then I should make sure that my opponent was too.
But I learned my lesson and you would like to think that Scott Brown will absorb something from Tuesday night's red card against Barcelona.
You can dress it up whatever way you want, but the bottom line is that it was stupid. He must know that himself and for all that he may feel as though he was hard done by, the fact is that the referee was in close proximity to the incident and was really left with very few options.
Yes, he had a yellow in his hand for the original foul but the flick out at Neymar was always going to end with Celtic losing their captain. The Brazilian went down like he'd been hit with a missile from the stand, but the point is that the referee's interpretation of the incident will lie in the fact that there was intent.
I do think Neymar is an outstanding talent but Barcelona have never been noted for that kind of play. Lionel Messi is probably one of the most fouled players in the world but by and large he dusts himself down and gets up and on with it. So I think there was a lot of resentment at the way the forward made such a meal of things - but it shouldn't detract from the issue that Brown was guilty of being really stupid.
And for that reason I see very little reason for Celtic to do anything other than suck it up and bury it now.
There is no justification for an appeal as to me Brown was in the wrong. He will miss the Ajax game at the end of this month, with the club learning on October 17 if that one match ban will be extended.
You are never too old to take any lessons on board in football and Brown has to take something from this.
Prior to his dismissal, Barcelona had not actually created too much. That changed when the game opened up a little after Celtic went down to 10 men and then when they lost a goal.
The satisfying thing for Neil Lennon will be that even after going a man down there was still a lot of positivity about Celtic.
They should really have taken the lead before Barca went up the park and scored. Charlie Mulgrew will still be reliving his header. He will know more than anyone that he should have scored.
I actually thought that Celtic played better against Barcelona on Tuesday night than they did when they beat them in Glasgow last season.
Even when the fourth official indicated that there would be four minutes of added time, you felt that Celtic could still have it in them to get an e qualiser. But ultimately at this level when you create chances, you must take them.
It leaves them now looking at the game against Ajax at the end of this month and knowing that they must take something from it.
I don't imagine that they will go into the match with too much trepidation since they have acquitted themselves well against both AC Milan and Barcelona. There will be real disappointment that they do not have a point to show for their efforts.
For me, no-one quite epitomised those efforts the other night quite like Georgios Samaras.
His effort, determination, bravery - words that no so long ago we would rarely have used in connection with the Greek forward - were all to be commended and I thought he played out of his skin.
He tried to do a lot on his own but the sheer work-rate and desire from him was excellent and I take my hat off to him for that.
I have not always been his biggest fan, but he seems to relish these big European nights and over the last few seasons he has been outstanding at that level.