Prince William has warned social media negatively impacts young people's self-esteem and confidence.
Speaking at a children's charity gala, the Duke of Cambridge said children and young people are increasingly under pressure compared to past generations.
The event at the Roundhouse in north London was raising money for the Children's Trust, which helps children suffering from brain injuries, and SkillForce, which works with ex-service members to teach young people resilience, leadership and self-esteem through mentoring and workshops in schools.
It was hosted by David Walliams, who is an ambassador for the Children's Trust.
"Children are tested more than ever before and are being prepared to enter a highly competitive work market," said Prince William.
"On top of this, there is a sense of being 'on call' 24/7 through social media, and the subsequent strains this can have on relationships, home life and, ultimately, a child's sense of their own self-worth. It can all take its toll.
"Role-modelling and giving a child the tools of courage, discipline and resilience are a demonstration of great love and commitment to that child's success in life.
"If you are not taught these skills at a young age, it can be very, very difficult to learn them as an adult."
The event marked the launch of the Prince William Award, which is aimed at helping children aged six to 14 develop their confidence.
Guests included Jennifer Saunders and Dawn French, actress Vanessa Redgrave, singer Elaine Paige and cricketer turned presenter Phil Tufnell.
The Duke and Duchess of Cambridge, along with Prince Harry, are campaigners on children's mental health, and have been involved in work towards removing the stigma around young people's mental health through the Heads Together campaign.