0 used to mean that it is easy to understand what you could have done to prevent something bad from happening after it has happened: --
In retrospect, we should have insisted on checking his calculations, but it's easy to be wise after the event.
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Vi kan slutföra det steg för steg hur lång vägen än är och den kan inte slutföras hur kort vägen än är om du inte ens markerar ditt fotavtryck.