Olivier Giroud was "angry" with himself for forgetting he had already been booked when he whipped off his shirt to celebrate scoring Milan's late winner against Spezia.
Giroud came off the bench to snatch a 2-1 victory for the Rossoneri with an 89th-minute volley after being picked out by a superb Sandro Tonali pass.
The France striker was then given his marching orders, having been shown a yellow card six minutes before scoring his decisive goal.
Giroud has been in the thick of the action this week, scoring two goals and providing as many assists in a 4-0 thrashing of Salzburg that put Stefano Pioli's side in the Champions League round of 16.
The 36-year-old was frustrated that his earlier caution had slipped his mind after his clinical finish in the closing stages at San Siro.
"It was certainly a very nice goal, which came thanks to Tonali's assist," he told Sky Sport. "We wanted to win this match, the important thing is to have three points more in the standings but I'm angry because I forgot about the first yellow card."
Asked if he was not thinking clearly due to the ecstasy of scoring the winner, he replied: "Yes, football is like that. The adrenaline and the happiness of having given victory to the team after a difficult match has affected me.
"In my head I am still a child, but I have great faith in the team and also on Tuesday [against Cremonese] we will fight to win the three points."
Theo Hernandez put Milan in front with a first-half volley from close range, but Daniel Maldini equalised against his parent club with Spezia's first away goal of the season.
Tonali had a goal ruled out at 1-1 for a foul on M'Bala Nzola by Fikayo Tomori following a VAR check, but Giroud moved them six points behind Napoli in second place after the leaders beat Atalanta 2-1 earlier on Saturday.