The weakest link in the chain is the point at which the intended journey from A to B veers off at C.
* Blondin, halfway across Niagara, is distracted by a seagull and is sidetracked to the rocks below.
* The white grains stirred into the tea were salt and not sugar.
* The best football team chose a goalkeeper who urgently needed an eye-test.
* Some time in the early centuries AD, the Christian hermits and ascetics who had retreated from the world into the desert accepted and acquired a taste for temporal power (ignoring Jesus' advice that you cannot worship God and Mammon). At this point Christianity was grafted onto the tree of Jesus' teaching. The entirely different kind of fruit which has resulted is clearly seen in the jungle world of today and also in the history of the Churches' activities (wars, suppression, Inquisition, torture and accumulation of wealth et cetera.)
* You answer your mobile on the motorway and reach home later than intended (via the back of a truck, a hospital and a stretcher).
Every time things don't turn out as expected, look for the weak link in the chain of events and take precautions for next time!
NEW PROJECT: LET THEM HAVE ENOUGH ROPE AND THEY WILL HANG THEMSELVES!
(NO NEED TO DRAG THEM SCREAMING TO THE SCAFFOLD.)