I was reminded recently of an entertaining little book, the Extraordinary Popular Delusions and the Madness of Crowds, published in 1841 by Charles Mackay - not at all to be confused with the more pithily-entitled The Madness of Crowds, published in 2019 by Douglas Murray. Both books are gripping reads, and you may be encouraged to learn that the older one is still available as a reprint - of course, both are significant in the way they provide a useful commentary on our crazy world.
Mackay's slim volume has long since found its way to a charity shop (my wife is a ruthless tidier of over-stuffed shelves), but I remember it well. It details several examples of speculative lunacy, including the South Sea Bubble of the 1720s (initiated by the British Government, to finance the war with France), and also the Dutch 'Tulip Mania' of the 1630s, where, almost overnight, tulip bulbs became commoditised to the point where a single specimen of Semper Augustus could command a price of ten times the annual salary of a skilled craftworker.
Each of these is an example of a bubble, the kind of bubble which would require a kind of 'commonsense-bypass' operation to be able to ignore the very high likelihood of a collapse. There are several interesting observations to make about these phenomena: firstly, the Dutch economic and financial system was living through it's 'Golden Age' at the time - there had never been an infrastructure anywhere on the planet as advanced and as sophisticated as this one was at the time. The price of the bulbs skyrocketed because of speculators in 'tulip futures', prior to the catastrophic collapse in 1637. It is clear that the technical excellence of the marketplace provided no protection against a toxic brew of idiocy and greed.
Secondly, it is worth noting that neither educational background, or sheer intelligence was any kind of protection. The world-famous physicist, Sir Isaac Newton, invested heavily, then (wisely) got out of the South Sea Bubble and then (unbelievably) invested again, shortly before the collapse. In the process, he lost a colossal sum by today's standards. Had the FOS existed back in 1720s, no doubt he'd have been queuing up for his share of redress - and it's worth noting that 462 members of the House of Commons and 112 Peers were all involved in the South Sea Company. This bit of background may help influence your approach when it comes to recommending an investment solution that your clients are capable of understanding and working with.
Thirdly, the reason I was thinking about these two historical phenomena (again) is because I have been reading Frank K. Martin's 2006 book Speculative Contagion, wherein he refers to these, and other (much more recent), examples of the kinds of behaviours which financial-planners and advisers really ought to have nothing to do with. The strange thing is that, all too often, there are those amongst us who somehow can't resist dipping their toes into this kind of ill-conceived speculation. These are folks who managed to time the market right on a couple of occasions, and on that basis have persuaded themselves that they can walk on water, rather than absorb the rather more valuable lesson that on this occasion they got lucky. Perhaps they genuinely believe that an aura of divine infallibility surrounds them, so that the normal mishaps of life, or the laws of the universe will somehow pass them by. Clearly, one doesn't want to discourage self-belief, but there must be some kind of dividing line between that, and the kind of pathology that requires therapy.
Fourthly, and as perhaps a slightly trite comment, it is worth observing that there is a reason why history appears to repeat itself: nobody listens.
My personal tip in relation to tulip bulbs: buy them from a reputable specialist supplier or garden-centre, plant them in November, after the first frosts, in well-drained soil. Then sit back and wait for that glorious moment in the Spring when the magic happens.