When you're sad.
The doctor has you lie with her on the sofa while you watch a film and she cuddles you until you feel better. Should that fail shell just scoop you up and shower you in affection.
When she's proud of you.
She will pick you up and spin you around, nothing makes her happier than when she sees you take control and use your brains to defeat aliens that have very little to no brain cells.
Just random hugs.
Sometimes she will stop what shes doing, even in the middle of important things and hug you tight. It normally lasts a while and catches you off guard, but those are the moments you live for.