This realisation struck me dramatically this week in the crucible of the squash court - a rectangular white space more like a cell in an imaginary lunatic asylum than any other room I frequent, where sounds and emotions bounce back at you off the walls like the ball itself.
I had returned to the court for the winter season last month, feeling fit, confident and raring to go after a summer of outdoor activity. But my matches have already resumed a wearily familiar pattern. I have lost them all (and if losing is supposed to be better for you than merely winning, why does it feel so grim?). You may suppose that I lose simply because I'm bad at squash (which indeed I am), but it's more complicated than that. After all, we're carefully graded by the club to come up against players of roughly the same standard. No, with me it's a mental problem.
Each match follows the same pattern. I step on to the court with a stranger. We warm up, and I run through the check-list of Things To Remember: racket back early, eye on the ball, hold my position on the T, don't just belt it - think. We begin, and match each other stroke for stroke, point for point, until about five-all in the first game. Then I roll over and let my opponent win, usually 9-6. Repeat twice, and my opponent has won the match three games to nil - as easy as that, week after week.
I've tried to work out what's going wrong. Is it that I try too hard and snatch nervously at the ball instead of striking it with confidence? Or perhaps I don't try hard enough, and mess up through slackness? And why do I spend so much time feeling sorry for my opponents, for quite contrary reasons? If I win two or three points in a row, and even manage to take the lead, I invariably ease up to allow them back into the game and end up losing. Conversely, if they get ahead I feel the need to apologise for not putting up a better struggle, for wasting their time.
At some point - and this is where it gets truly embarrassing, not to say revealing - I decide that I'm being too laid back, that I just don't care enough, and that the only way to put up a better fight is to get angry with myself. So I start staring wide-eyed at the blank walls and shouting at the top of my voice - "Pull yourself together, Bruce... get on your toes, for God's sake!" - carrying on in front of a total stranger in the way that is usually reserved for family consumption. At the same time I remain as polite as possible - "brilliant shot", "would you like to play the point again?", "was I in your way?" - just in case my opponent is beginning to think I'm a bad loser.
My opponents - mild-mannered computer programmers, property consultants, accountants, set designers - behave in much the same fashion (although it is much easier to be graceful in victory than in defeat). If I manage to force a string of errors from them, they start admonishing themselves in louder and louder voices: players who have introduced themselves as Jim or Mike take on the tone of a stern parent: "James!" they bark at the wall, or "Come on, Michael!". One punctiliously polite German acquaintance launches a Wagnerian aria of angst with the roar: "Maaaann... !" - and on a busy lunch hour the club's 10 courts echo with the wails of a score of suffering souls, each cursing his own shortcomings.
I haven't worked out whether we are the better or the worse for this. Have we found a harmless release for the pent-up aggression of stressed-out urban life, emerging cleansed from the catharsis of the squash club? Or are we quite unnecessarily adding another layer of mental torture to the strains of everyday existence?
What I do know is that I haven't picked a fight with a total stranger in recent weeks, but then most people who never set foot on a squash court do not either.
And, having no cat to kick, I do tend to shout at my children with alarming frequency. But most of all, I know I would love to win at squash, just occasionally. The club already has a physiotherapist, but what I need is a shrink.