The Stadio Olimpico clash hands Roma the chance to immediately cut Juventus' gap at the summit back to one point after Massimiliano Allegri's men signed off before the mid-season break by beating Cagliari on Thursday.
Milan are fresh from an impressive 2-0 home win over Napoli, but Garcia is in defiant mood ahead of the visit of Filippo Inzaghi's side.
He said: "The more they bother us, the more we'll fight. The more difficult it gets, the more we'll attack. Case closed.
"It's the last home match of the year and we'll be doing everything we can to put three points under the tree.
"We need to play our game and be ambitious, both psychologically and in terms of our attitude on the field.
"It's my second Christmas here, but nothing's changed from last year. The ambition is the same: to win."
Garcia also confirmed that he will on Friday contest the charge levelled against him regarding an alleged incident with a steward after the Genoa match last Sunday, which saw him handed a two-game ban.
"To be judged and sentenced without giving my side of the story is something I've never seen before," he added.
"Nothing happened in Genoa and we'll be appealing. I can't say anything more on the matter."