An odd thing to be sad about I know.
It hits me every now and then that I'll never travel back in time - I was reading a book about a local biscuit maker the other day (riveting, I know) and they listed a few of the old biscuits that they stopped making after the war, and commented how we'll probably never know what they tasted like - my immediate thought was 'ooh when I go back I'll have to try some of these, they sound interesting'. Then the obvious fact that that's never going to happen hit me and I felt a bit glum 
It happens for loads of random things, I think 'when I travel back to Roman times I'm going to ask Catullus x' or 'I'm going to go see Aristophanes' Frogs when he first puts it on' or 'I'm going to visit the singing statue of Memnon when it still sang' etc...
Completely barmy I know, but AIBU?