The South Korean midfielder felt one lapse in concentration cost the Red Devils dearly at Anfield, after they controlled the ball throughout the game
Park, who scored United's goal in Saturday's 2-1 fourth round FA Cup loss to Liverpool, said the Red Devils would now focus on the Premier League and Europa League, having been knocked out of three competitions already this season.
"We must quickly forget about this game, move on and look to the future," Park told MUTV. "We still have the Premier League and the Europa League to focus on."
Park said United arguably deserved better from Saturday's loss at Anfield, admitting a late lapse of concentration cost them for Dirk Kuyt's winner.
"We controlled the ball which is what we wanted before the game. We did that well but that couldn’t get the win for us," Park said..
"In the team meeting, we talked about trying to keep possession and then make chances. We did that and that’s why we played very well.
"But then we lost concentration for a moment and ended up giving them the goal to make it 2-1. Everyone was quiet afterwards because we all feel disappointed."