The Rouge et Blanc were beaten 2-1 at home by Valenciennes on Friday and the Colombian striker, who missed a penalty, was unhappy with how his return from injury panned out
The Rouge et Blanc were beaten by an own goal from Eric Abidal and a cool finish from David Durcourtioux, with James Rodriguez's late header merely a consolation.
Falcao, 27, made his comeback from injury off the bench but failed to help his side salvage anything from the game at Stade Louis II, missing a penalty in the closing stages prior to James' goal.
"I came back with a lot of desire, but unfortunately we missed all of our opportunities," the Colombia striker told reporters after the game. "I missed a penalty, for instance.
"This kind of match leaves a very bitter taste in the mouth. But, if we take stock of the season so far, we do not need to worry like crazy.
"We must remain calm, serene and continue to work to come back stronger after Christmas."
Monaco sit second in Ligue 1 but have played a game more than Paris Saint-Germain and Lille, who sit two points above and below Claudio Ranieri's side respectively ahead of their meeting at Parc des Princes on Sunday.