Jo Grant: So I waited, I waited because you said that you’d see me again. You did. I asked you and you said yes. You promised so I thought one day I’d hear that sound, deep in the jungle I’d hear that funny wheezing noise and a big blue box right in the middle of the rain forest because he wouldn’t just leave. Not forever. Not me. I’ve waited my whole silly life.
Doctor: Aw then you’re an idiot. No, no, no don’t you see. How could I ever find you? You spend the past forty years living in huts, climbing up trees, tearing down barricades. You did everything from flying kites on Kilimanjaro to sailing down the ansee in a tea chest. Not even the TARDIS could pin you down.
Jo Grant: Hold on I did sail down the ansee in a tea chest, how did you know?
Doctor: That family all seven children, twelve grandchildren, thirteenth on the way. He’s dyslexic, but that’ll be fine, great swimmer.
Jo Grant: So you’ve been watching me all this time?
Doctor: No because you’re right. I don’t look back because I can’t. But the last time I was dying, I looked back on all of you, every single one, and I was so proud.

I love the idea that we don’t get to see everything the Doctor does. Like at the end of The End of Time Part 2, when he checked on all his former companions, we saw the ones that mattered to us. We saw the new ones, but that doesn’t mean he didn’t go see every single one of his former companions. It’s nice to know that there are some things we will never fully know about the Doctor and what he’s been up to.