In season 8 episode 4, Listen, after they were at the end of the universe and the Doctor is knocked out, Clara uses the TARDIS telepathic circuits to escape. They end up in a barn. Clara checks out the situation and hides under a bed from the parents of a child who is present in the barn. Then she realizes the child is the Doctor and tells him something to always remember:
CLARA: Listen. This is just a dream. But very clever people can hear dreams. So, please, just listen. I know you're afraid, but being afraid is all right. Because didn't anybody ever tell you? Fear is a superpower. Fear can make you faster and cleverer and stronger. And one day, you're going to come back to this barn. And on that day you're going to be very afraid indeed. But that's okay. Because if you're very wise and very strong, fear doesn't have to make you cruel or cowardly.
CLARA [OC]: Fear can make you kind.
CLARA: It doesn't matter if there's nothing under the bed or in the dark, so long as you know it's okay to be afraid of it.
CLARA [OC]: I'll show you. So, listen. If you listen to nothing else, listen to this.
CLARA: You're always going to be afraid, even if you learn to hide it. Fear is like a companion. A constant companion, always there. But that's okay, because fear can bring us together. Fear can bring you home. I'm going to leave you something, just so you'll always remember, fear makes companions of us all.
Then she went back to the TARDIS and said:
ORSON: What happened? What did you see? What's out there?
CLARA: What if there was nothing? What if there never was anything? Nothing under the bed, nothing at the door. What if the big bad Time Lord doesn't want to admit he's just afraid of the dark.
DOCTOR: Where are we? Have we moved? Where have we landed?
CLARA: Don't look where we are. Take off, and promise me you will never look where we've been.
CLARA: Just take off. Don't ask questions.
DOCTOR: I don't take orders, Clara.
CLARA: Do as you're told.
Why did the TARDIS take them to the Doctor as a child and why didn't she want the Doctor to know were they were? What did he see when he was knocked out? Why did she say that speech to him as a child? I thought the speech was to know his future was in safe hands as his future regenerations Hartnell-Capaldi.