If we are speaking in the most general of senses, the concept of "re-energize" speaks to resurgence. It seems to me that it indicates that while conditions are trying and while individuals might lose zeal and passion, there is a level where to which they can aspire that reflects intensity and complete commitment. The idea of "re-energize" indicates to me that someone at one point possessed energy and enthusiasm. Time or conditions might have worn them down, causing these elements to decrease. In the end, the idea of being able to rekindle these sparks into a fire is what determines the ability to "re-energize" and within this is something that helps to greatly increase one's capacity to be human. The resurgence of energy is what makes one distinctly human, something that speaks to the great quality of an individual being.
The word 're-energize' literally means to 'revive' or 'recharge.'
It is a fairly recent addition to the English language. It is used in a context to stir someone into concrete action. Imagine a situation in which things somehow seem to drift along listlessly and the expected results do not materialize, then the leader of the group motivates his team by offering them incentives to make his team members more focused and productive. He tries to revive their interest and motivate them to achieve their goals. The following sentence will make the meaning clearer:
'The campaign manager encouraged and re-energized his team by offering them bountiful incentives to be paid on completion of the task.'
It is important that one always performs at his best. To do so, motivational talks, and performance linked incentives go a long way in 're-energizing' people.