A mistake from defender Eder Militao gifted Getafe's Enes Unal an early goal at the Coliseum Alfonso Perez in the first LaLiga match of 2022.
Luka Modric hit the post and Casemiro had a shot well saved by goalkeeper David Soria -- who also kept out substitute Isco's late header -- as Madrid experienced defeat for the first time since October.
"We gave away the first goal, from a player (Militao) who usually stands out in defence," Ancelotti said in his post-match news conference.
"There isn't much to say about the game, we just stayed on holiday for one more day. The team didn't look like the one that played before Christmas."
Real Madrid went into the match on a 15-game unbeaten run in all competitions, while opponents Getafe had only recently climbed out of the relegation zone.
"We looked like another team, with less concentration, less commitment," Ancelotti said.
"We didn't deserve to lose of course, a draw would have been fair, but we gave away a goal and you end up with a loss. It could be a wake-up call. Today the team was on holiday."
Despite the setback, Madrid have built up enough of a lead at the top of the LaLiga table that they remain eight points clear of second-placed Sevilla -- who play on Monday -- although Ancelotti's side have now played two extra games.
"Preparing for these games after Christmas, with players who travel, isn't easy," Ancelotti said. "But talking about that would be looking for excuses, and I don't want that. We didn't play well.
"I said exactly the same thing to the players. We take responsibility. Maybe the coach was on holiday too. We take responsibility. But no dramas, no criticism, no tragedies, because we're still leaders."
Real Madrid travel to Alcoyano in the Copa del Rey on Wednesday -- having suffered an embarrassing cup defeat to the same side in January 2021 -- and then host Valencia in LaLiga next weekend.
They then travel to Saudi Arabia for the Spanish Supercopa in a busy start to the new year.