Referee Mr Styles pointed to the spot but Manuel Almunia guess right and saved Robbie's penalty. Three minutes later Arsenal netted what turned out to be the winner.
"Obviously we are disappointed because we feel we came and took the game to Arsenal and I think for periods of the game we were the better side," reasoned Robbie. "When we got back level I thought we were going to win it.
"Unfortunately I missed the penalty and they went up the other end and scored. That is how football can change so quickly. While there is disappointment we can take a lot of positives from it," added Robbie, who insists the missing of his spot-kick will not affect his confidence.
"You just have to get on with it, simple as that, there is nothing else you can do. Of course I am disappointed like everyone else, disappointed for the players because we worked very hard to get something out of the game and the fans.
"I am experienced enough to understand that you get great days but you also get some bad days - this was one of those days."
Robbie Keane reflected on the quickly changing nature of football after the 2-1 defeat to Arsenal at the Emirates Stadium on Saturday.The team forced the issue after falling a goal behind shortly after half-time and levelled through Dimitar Berbatov following a sustained spell of pressure. The home side were then rocking and the Bulgarian was chopped down in the area by Kolo Toure.