Hart, 29, was criticised for shouting and swearing in the tunnel before tournament games in France.
The Manchester City player made mistakes against Wales and Iceland before England went out in the last 16.
"The Euros wasn't my finest hour, so I needed to have a think and pick apart how I played and what I did," he said.
Hart was at fault against Wales when he let Gareth Bale's free-kick to squirm under him in the 2-1 win.
More crucially, he failed to stop Kolbeinn Sigthorsson's winner in the embarrassing last-16 defeat by minnows Iceland.
Media playback is not supported on this device
Hart lost his place in the Manchester City team under new manager Pep Guardiola and has since been loaned to Italian side Torino.
He remains the number one choice for his national side and made a series of stunning saves in last month's World Cup qualifying draw in Slovenia.
"I've got a lot of energy, a lot of passion," said Hart. "It could have been too much.
"There's nothing wrong with being positive. Being passionate and proud of your country is definitely a positive - but there's different ways of channelling it. I've looked into that and hopefully it will help.
"I'm constantly changing and evolving, trying to be the best I can be. Learning from things that didn't go too well is definitely a way of doing that."
England keeper Joe Hart is trying to "channel" his pre-match energy and says he could have been over-hyped during the team's Euro 2016 humiliation.