Serious Simon and Emotional Elizabeth use the Time Barrier to travel to different doctorwhoish pasts and presents, never meeting the Time Lord himself, of course, but sometimes meeting versions of themselves and their families.
Old Beth: Sometimes in life you have to make decisions and hope they come out for the best. You’ll know about that soon enough.
Young Liz: But I’ll never make your decisions, will I?
Old Beth: Then how did I come to make them? We’re the same, Liz. But I’m like a person You’ll never be, and you’re like a person I never was, never.

Variants

(1)
  1. Timeslip by Ruth Boswell and James Boswell (28 September 1970).
    2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Ruth Boswell
    James Boswell