Its manifestations are legion, and we can't be prepared for all of them; its vagaries can leave us scrambling for the right words, as the skill of extemporaneous dissembling, like most practical skills, is not taught in the textbooks.
'I'm bucked, doctor,' said Jimmy from his sick bed, and I reckoned his assessment was pretty accurate.
When I went outside I found the whole family assembled, and the babble of conversation ceased instantly. The clan had gathered and relatives had winged their way from the four corners of the world; two or three of the more distant second cousins were hanging expectantly from the rafters.
'How is he, doctor?' asked his wife anxiously, at the same time setting before me a plate of egg-and-onion sandwiches more than two feet high and a scalding-hot mug of tea as big as my head.
I paused, aware that they were hanging on my every word and that it is impossible to speak clearly and with an air of authority while swallowing a mouthful of egg and onion. There was a long silence, broken only by the cheerful sound of mastication.
I was also aware that words were quite inadequate in this situation. Even the English language, with all its meandering glory and subtle nuances and richness of texture, would have difficulty conveying that there is a sick old man in there, I'm sure he's dying, all systems are failing, heart, lung, kidneys, brain, you name it, and although I'm doing my best to keep him comfortable, I don't really know what's going on, perhaps only that doing nothing heroic is absolutely the right thing; don't really know what's wrong with him, pay no attention to what I write on the death certificate, it's only a best guess; and most of all I don't know how to explain my uncertainty to you because I know it's not what you want to hear right now.
You want someone strong and certain and positive, someone who knows what is happening, someone in control, someone like John Wayne.
So: 'Mary,' I said gravely, placing a firm, supportive hand on her shoulder, just like The Duke would have done, in the hope that my body language might help disguise the poverty of my words, 'I'm afraid he's bucked.'