I once had a bloke with obvious learning difficulties that had a long conversation with me about how unhappy he was, how lonely he was, and how his parents were both ill.
I was going along with it with the basic "oh yeah. yeah. terrible" because I'm very reserved/shy etc, until he leaned in to cry on my shoulder.
That's my bloody limit.
Another guy, much the same, started talking to me on the bus about where I was going, where I'd been, where would I be on xxx day, telling me I couldn't pronounce the name of my town, asking me whether i'd been to manchester, liverpool, bath [insert obscure places here] and then asking me odd questions like "I don't think someone from manchester would come here [oxford] do you?"
wtf was he on about? Every time I replied he lit up like a bloody christmas tree he seemed so happy.