One thing that bugs me a bit: If I am taking a few minutes to stop to talk to a coworker that I also consider to be a friend about something, and another coworker just walks up to the cube and invades, bringing the conversation to a halt. Call this my smoke break. If I go silent when you walk up, you can safely assume you weren't welcome into what I was discussing.
Yesterday this happened (again) interrupting a conversation I had no plans on sharing with the third party that interrupted, so I just got up and left. Then I stewed a little, because this person does this fairly often to me. I admit I'm not this person's biggest fan, so is that what peeved me about it? No, not entirely, I don't like it when others do it either if I am in the middle of something that I've lowered my voice to say (read: confidential) or something that I am having emotion over (read: private).
I had an epiphany later in the day. I think what really exacerbates the issue and peeves me so much is when I am already feeling lonely and then I get cut off from someone I was talking to. That conversation yesterday was the only one I had face to face with someone other than ordering food when I went out for lunch and when I talked to another coworker for 10 minutes about work stuff later in the day (and this was on the phone). The rest of my conversations yesterday were typed or with my dogs. The people who interrupt? You go home to your family and can chat chat chat. Please, cut me a break. I just wanted 5 minutes with another human being.