Jurgen Klopp admitted he was angry with Liverpool's performance after they slumped to a 2-0 defeat at West Ham.
Headed goals in each half by Michail Antonio and Andy Carroll made it back-to-back wins for the Hammers and ended Liverpool's Christmas revival.
"It's no day for being disappointed, it's a day for being angry," Klopp told BT Sport after the game, and that emotion lasted until his full press conference.
Klopp felt left-back Alberto Moreno was fouled in the build-up to West Ham's 10th-minute opener, when Antonio thumped in a close-range header from Enner Valencia's cross.
But he was even more annoyed with his side's defending nine minutes after the break, when Mark Noble's floated cross was powerfully dispatched by Carroll against his former club.
"It was five against one, near the sideline, and nobody won the ball," said a disbelieving Klopp.
"Then cross, Andy Carroll, 2-0, thank you very much! If you know the other team has Andy Carroll, how can you allow crosses?
"It was not enough from my team today. The decisive moments we were there, but we were not there 100 per cent.
"We could have done much better. We had our moments, we tried, but if you fight at 95 per cent then it's not enough.
"It's my responsibility. I'm angry about myself today."
West Ham could have scored more, with Manuel Lanzini hitting a post with a vicious, swerving drive and Simon Mignolet saving well from Aaron Cresswell's deflected shot and another Carroll header.
Yet Liverpool could still have snatched something from the game, as Emre Can hit the crossbar at the end of the first half and Lucas had a header cleared off the line towards the end of the second.
But the day belonged to Carroll, who celebrated wildly after scoring a goal against the club who let him leave just 18 months after signing him for £35million.
"I thought he was brilliant," said Hammers manager Slaven Bilic.
"Not just because of his goal but his performance; defending, holding the ball up, pressing their defenders, everything.
"Liverpool is always a 'target' team, especially now with Jurgen Klopp as their manager, and to create chances and keep a clean sheet is a great way to start the new year for West Ham."
The only sour note for West Ham was an injury to Lanzini, who could face another spell on the sidelines after he suffered a recurrence of the thigh problem which kept him out for the last two months.