I tend to think things through a lot. While I've learned to cope with -- indeed, even enjoy -- spontaneous situations, I don't tend to encourage them. When I expect something to happen, I think it through repeatedly. I ponder what problems might occur, and how to deal with them best. Most relevantly, I think about what other people might say, and how to respond to them.
The problem is, much of this musing is utterly pointless: I think through many interactions that never really occur. Indeed, in most of these cases, no conversation even remotely like what I've imagined happens. People are simply not as predictable as events, and conversations too chaotic.
Meanwhile, though, I will often work myself into a positive frenzy over bad interactions that never happen. In many cases, I can actually make myself a shade paranoid, simply because of thinking about the despicable things that someone might (but usually doesn't) say. These mental arguments tend to get far more heated than any real ones do, and tend to bring my blood pressure up, entirely without good reason.
I'm pretty sure I understand why I do this: it's a fairly natural reaction to "what I shoulda said was...". But on balance, it seems to have much more negative effect than positive -- I'm rarely correct in my fevered imaginings, and it's just plain unhealthy to send myself into fight-or-flight mode with no good reason.
So, something to work on. It isn't easy: not thinking along these lines is very much like not thinking about the proverbial elephant once it's been mentioned. But one can't effect mental change without working on the mental discipline. I need to trust myself a bit more, and focus on responding well to events as they occur, rather than trying to control them in advance.
(I must admit, the more I think about the mental disciplines I'm looking for, the more I suspect I need to delve more into Buddhism. I know just enough to know that there are some forms of it that match my worldview fairly well, and the mental goals are mostly ones I find admirable. A long-term research project...)