The thing that is at the same time the hardest and easiest to do is what needs to be done.
|English: Footbridge over Garden The public footpath crosses a nice little footbridge which goes right over the centre of a delightful private garden. An excellent solution to a difficult problem (Photo credit: Wikipedia)|
It is maybe because the solution wasn't hard to begin with but was just a difficult choice. The reluctance to choose that solution or reluctance to put the solution in motion, makes the problem feel so much harder.
So, the quote above distills the quandary to it's essence. It tries to capture this situation into wisdom that can re-used. It provides a cheat-sheet to those looking to solve a problem or choosing the best one: find the solution that the hardest to choose and easiest to do because it is likely the best one.
Sorry for the verbosity. The result of watching too many episodes of Elementary