I was having long thoughts again this morning on the way to work. It occurred to me that pretty much all the things I'm most afraid might go wrong with my life are internal to my own mind.

Falling inconveniently in love is perhaps the prime example: this has been a major source of woe to me in the history of my life. When I was a teenager and an undergrad I had a pretty much solid pattern of falling for someone I couldn't have, angsting about it for too long, eventually getting over it (usually by making a fool of myself in front of her), and then repeating the cycle with someone else. I don't seem to have been making quite such a career of it in recent years, but it still happens to me occasionally. And as if to make up for the relative infrequency, the last time it happened (a couple of years ago) it was worse than ever: it turned my brain completely inside out, disrupted my life utterly, and prevented me concentrating on absolutely anything at all – and it was only by great good luck that the worst of it only lasted a week and not months. So I still think of it as a clear and present danger to my mental equilibrium.

My other big worry is about losing my ability to do useful things with computers. Not so much my actual programming skills and knowledge – I've proved to myself any number of times that those are deep-rooted enough to survive practically anything I can do to my brain, up to and including balance-impairing quantities of alcohol – but the powers of concentration and focus that are necessary in order to apply those skills and knowledge to achieving any worthwhile goal. At work I don't feel as if I'm concentrating as well as I used to (although this may simply be because my job has been changing a lot in the past few months and I'm not used to it); in my free-software activities I seem to have been flitting about doing small and silly stuff, and it's difficult to imagine myself ever again having the time or energy to achieve anything of the magnitude (or the usefulness to society) of PuTTY.

Added to those there's a list of more minor mental worries: fear that the anxiety attacks I suffered a few years ago in the wake of a stressful life event might recur, fear that my ongoing difficulty convincing myself that I really locked the front door when I went out1 might be a symptom of the onset of some sort of OCD-like inconvenience. And, of course, fear that all this unnecessary worrying isn't good for me!

What strikes me as odd about this is that it's not as if there aren't plenty of things that could go wrong with my life in a purely material sense. I now own a house which might fail in difficult and expensive ways; I have a slightly rickety body which might at any point choose to develop some new and exciting ailment to help make a mockery of the idea of Intelligent Design; and there's always the background risk of things like car accidents, people close to me dying, and so on. For some of these things the actual risk (probabilistic expectation of the total damage to my life) is probably higher than the purely mental phenomena I've listed above.

But none of them scares me nearly so much as the mental risks. I'm not sure why. Perhaps it's because I perceive (with dubious accuracy) my mind to be under my own control, so that if it does something wrong or unhelpful then it's in some sense my fault, so I feel as if I should be taking extra care in pre-emptive avoidance. Whereas many of the material and physical risks to my life are things which it's easy to see as basically unpredictable, so while they could strike me at any time there would be less of a feeling of having ‘done it to myself’, and more a feeling of ‘them's the breaks, these things happen’.

1. Which seems to be worse in the new house, incidentally, as a result of the way the front door lock works. I plan to get a new front door, since the behaviour is annoying for other reasons too, but haven't got round to it yet.