Definitions
nenji: unusual/ mysterious/ shocking occurence
vara: peculiarity
Translation
A shocking occurrence does not happen instantly; a number of peculiarities are witnessed ahead of it.
Application
A crisis or bad situation is often preceded by small undesirable incidents, building up over time. Only after the bad thing has happened do people manage to make sense of all the prior happenings. The message here is to be diligent enough to stop something before it has an opportunity to develop.