England captain Gerrard bagged the killer second goal in a 2-0 win over Poland at Wembley on Tuesday that earned Roy Hodgson's team automatic qualification for next year's finals in Brazil.
Wayne Rooney had opened the scoring just before half-time, but Poland had several chances to shock the hosts, who couldn't afford a draw, and Gerrard conceded England, who gave away possession too easily at times, must improve their ball retention to beat the world's best.
"The big lesson is to play better in the second half. We must keep the ball better when it gets tough," Gerrard said.
"But at times in the last two games we were fantastic. Tonight, we started really well and we are getting better defensively.
"We know there is a great togetherness in the squad, and that is all that matters. We performed under tremendous pressure."
Meanwhile, Rooney said patience had been key to England's success against the Poles, who featured prolific striker Robert Lewandowski and arrived with nothing to lose as they were already out of the qualifying race.
England's nerves were jangling at times as they tried to break down Poland in the first half, but the Manchester United striker claimed they always believed they would finish the job.
"A big part of our preparations was being patient. We knew they would come and make it tough," he said.
"We have always remained positive. We have had a great focus and belief."
With the road to Rio finally reaching a successful conclusion after some disappointing displays earlier in the qualifying campaign, Rooney is adamant England can go to the World Cup confident of making an impact.
"We have some fantastic young players in our team, with some great experience. It is a good blend, it is good times for England," he said.