Once upon a time, there was a general who was leading his army into battle against an enemy ten times the size of his own. Along the way to the battlefield, the troops stopped by a small temple to pray for victory.
The general held up a coin and told his troops, "I am going to implore the gods to help us crush our enemy. If this coin lands with the heads on top, we'll win. If it's tails, we'll lose. Our fate is in the hands of the gods. Let's pray wholeheartedly."
After a short prayer, the general tossed the coin. It landed with the heads on top. The troops were overjoyed and went into the battle with high spirits. Just as predicted, the smaller army won the battle.
The soldiers were exalted; "It's good to have the gods on our side! No one can change what they have determined."
"Really?" The general showed them the coin--both sides of it were heads.
In ancient times, man had to gather food for his survival. Success was not optional. He either found food or he died. As a result not only was his motivation higher but he was far more connected with his surroundings, and his group. Compare with 'modern' man. Modern man simply goes to the supermarket, and even if he is poor and homeless he still has social programs to help him. Modern society has worked to remove consequences from life and as a result, man has no connection with his world. He has no reason to neither connect nor even know who his neighbors are.
We end up with individuals who lack appreciation for who or what are in their lives. They lack respect, ethics and dignity, creating individuals who truly believe they are the only things of value, law unto themselves. This leads to a sapping of a society's collective will; ultimately culminating in a 'sheep' world of ignorant zombies, who eventually destroy all their enlightened individuals.
This command simply states that persistence is the key to success. We are minded that will is a matter of dedication, and motivation. Faltering motivation is the reason behind most failures. Not to say that all failures stem from a lack of will, because it is still possible to do all the steps right and still fail.
Human beings also seem to have trouble knowing what their will actually is. For example, consider a rapist. He commits a rape for the express purpose of the gratification of personal power, or the mating urge. However, his actions carry the penalty of imprisonment, which deprives him of the ability to sate his urges. Likewise with a thief, he steals for material gain, which carries the potential for him to loose all his material wealth. Neither of these individuals is properly expressing their wills.
Most people do not have a will; or rather they operate in an illusion of free will. Free will doesn't exist unless there is awareness and an understanding of the options available. You can be given an option to exit a room via different doors, but is it an option if they are all locked?