Rashford has scored three times in United's last two games against Southampton and Barnsley, rediscovering some of the form that saw him fire 30 goals in Ten Hag's first season at Old Trafford.
But the 26-year-old's performances dipped alarmingly last term after signing a new £300,00-a-week contract, and he was censured by Ten Hag for missing training following a 12-hour tequila bender in Belfast and going nightclubbing after United lost the Manchester derby in October.
Ahead of Saturday's clash with Crystal Palace at Selhurst Park, Ten Hag was asked if Rashford has learned from the experience.
He replied: 'I think he always knew, and every player knows, because when your lifestyle is not right you can't perform.
'You don't get the right levels when you don't have a good and disciplined life away from Carrington.'
Rashford has benefitted from Ten Hag's support and the guidance of his assistant, former United striker Ruud van Nistelrooy.
'Probably he needed some help, by backing him for instance,' added the United manager.
'At the end of the day, he has to do it by himself. He has to set his life right, his training attitude right, his match attitude right. When he sets his professionalism, he will perform because he is a class player.
'Marcus Rashford knows when there are setbacks how to get fightback, how to set his career, his performance. He took control of it and I think he is on the way back. He has started the season very good now he has to continue and to progress.'
The 26-year-old's performances dipped alarmingly last term after signing a new £300,00-a-week contract
Rashford pictured at a celebration event with friends, posing for the camera away from the football field
Rashford will be hoping for an England recall when interim boss Lee Carsley names his squad for next month's Nations League games against Greece and Finland.
Ten Hag said: 'I think he will always be an option for every manager, but it is not up to me.'