Conquering myself until

I've gotten so used to short, or frequently interrupted conversations at work, that now I can't seem to hold one for any length of time without getting squirrely, even when I'm actually talking to someone I know, about a topic of interest.
Recently, I was talking to someone who fits in that in between place; I know him at work, as in he comes in to the library pretty regularly, and we are friendly. We had previously had a conversation about a topic that had re-occurred while I was talking to someone else.
When I saw him yesterday, I began to reiterate the story, which was fine, but then I went on a tangent about adapting to anything pretty quickly, which led to talking about living in Japan and dealing with cultural differences, especially at my job, and that's where, I think at least, I lost him.
I pride myself, (and that in itself is a rare utterance from me,) in being clear, communicating well and being mindful of the context and recipient of whatever I'm running on about. Apparently, that's both somewhat unfounded, and a little vague.