England "have to build more relationships" as a team if they are to be successful in the future, says number eight Billy Vunipola.
The 22-year-old said England were "very carefully marshalled" during their unsuccessful World Cup campaign, which saw them go out in the group stages.
"It's a tough 12 weeks that we spent together," he told BBC Radio 5 live.
He said the best way to bond "is when you go out to the pub, have a drink and break down barriers".
The number eight, who was forced out of the tournament by injury, said that would help people "talk to each other about more than just who's coming to the hotel on Friday, or things like that".
"You want to get to know someone on a deeper level than that because when you are on the pitch, it helps," he added.
"I say that because when we play at Saracens that's what we do. It might look like a fun, jolly time but we build our memories together, we build bonds and bridges."
Asked if they were unable to do that during the 2015 World Cup, Vunipola suggested things might have swung too far the other way after England were heavily criticised for their behaviour at the 2011 World Cup in New Zealand.
"I think with the pressures of the World Cup after what happened in 2011 it was very carefully marshalled," he said.
"That's something we could have done a little bit better, but I had a great time with the team. I got to know a lot of people very well, I would have liked to get to know them better, not only that but their family and friends.
"That's something that's very important to me, I'm a very emotional player and I like to know who my team-mate is on a deeper level than just who his name is and who he plays for."
But Vunipola conceded that the players could have made a difference by being more successful on the pitch, instead of becoming the first World Cup hosts to go out of the tournament at the group stage.
"We didn't [have an amazing time] but we could have helped ourselves by making memories on the pitch," he said.
"It's just as important off the pitch to be together and stay close."
Listen again as Billy Vunipola joins Mark Chapman and Matt Dawson to discuss what went wrong at the Rugby World Cup.