depends on the context. it refers to energy, and adversity, and how there ought to be, or one can expect, some sort of need for or output of energy when there is a situation of conflict.
adversity is a situation of conflict of some sort. conflict tends to involve opposition of forces. forces are manifestation of energy. so, you need energy to carry on the conflict, or the side with the most energy is likely to prevail. Some people need adversity to get themselves to exert the energy that they already possess, some people find energy to carry on the conflict, ans some succumb to the overwhelming application of energy from the opposition.