Mark Hughes' side took a 2-1 lead in their League Cup clash with Reading on Wednesday, but conceded two late goals as they crashed out of the competition at Loftus Road.
The South Korean international feels the message is ingrained in the players, and is determined not to let it happen again.
He told the club’s official website: "After taking a 2-1 lead [against Reading], we lost concentration and conceded two late goals. We must not repeat this again.
"We scored twice and conceded straight away both times. If we want to win games, we have to be better after scoring goals.
"It’s not an excuse, but I know we can learn from that."
QPR's next test is against West Ham, and Park is hopeful of registering the club's first win of the season against the Hammers - but knows he and his team-mates are in for a tough battle.
He added: "It's a very big game, because we haven't won a league game. It's one that we want to get three points from – especially as we're at home.
"We need to win the game, everyone knows that. Everyone was disappointed by our result against Reading, but we have to recover quickly from that.
"It will be a difficult test. [West Ham] are a physical team and play in a similar way to Reading. We have to learn from that and show we did. There can be no excuses."