This is what I tell the kids at night as part of their bedtime routine:
John and I both say this to them:
Everybody loves you - and we name all the immediate family.
At the end, we say "You are special, you are wanted and you are loved. Right down to your core."
Sometimes I add in the following:
You are beautiful, strong, kind, smart and you can do anything you set your mind to do.
You have the power to make yourself happy.
Only listen to the nice things people say to you.
I really hope it sinks in for them. I want them to be strong, confident, happy people.