Jahrhunderthochwasser: (German) a flood of a severity that occurs only once a century.
Flood defences look excessively precautionary, overblown, paranoid, until an actual flood occurs. Then one is relieved and grateful that the flood defences are in place.
The work implied by the Steps similarly appears excessive until one finds oneself in a genuinely thorny situation: then one is relieved and grateful that the flood defences are in place.
Thorny situations could arise out of personal circumstances, what is going on in the world more generally, internal cycles, or just ‘because’. There is no predicting them, and there is usually no warning. By the time such a situation arises, it is too late to build flood defences: the flood defences have to be in place already.
With alcoholism, I need only one thorny situation in which my defences are not sufficient for the whole course of my life to be diverted into active alcoholism. My defences must therefore be strong enough to deal with the worst possible situation that might arise. A once-a-century-flood might indeed happen once a century, but the phrase does not mean one has to wait a century for the flood to take place; the flood could happen at any point during the century, maybe even today.
That’s why I have to be surrendered to God—in the place of my own assessment—today.