I had a chat with another librarian just before and we did ramble on for about 40 minutes about stuff to do with work. even though my issues couldnt be solved, at least she understood. I dont feel I can really 'talk shop' with someone who doesnt truly understand it.
with some people though you get the feeling they want to prolong the conversation with small talk and questions so I try to think of conversation stoppers like I need to go to bed now. What I mean is with friends is they do understand without you having to explain everything or spell it out. Thats the difference between a friend and a therapist, aside from paying them, a therapist will at most only pretend to understand what you are going through.