A healthy body with a lazy mind will eventually drag the body down. This will cause afflictions of the mind to flourish. Individuals who cultivate diligence have strong and healthy minds, and are more likely to also have healthy bodies, and they will feel elation in the Dharma.
According to one ancient treatise, there are three types of diligence. The first is diligence that is like armor; the second is the diligence that is able to gather all virtues; the third is the diligence that benefits all sentient beings.
Diligence that is like Armor
The diligence that is like armor manifests as fearless courage, enabling one to overcome all obstacles. One sees no enemy because nothing appears as an obstruction, and therefore nothing causes problems. One's diligence impels one forward fearlessly. When assigned a task, some people complain before even getting started. "Shifu, I see so many problems with this." These complainers see trouble rather than an opportunity. But there are others who take all impediments and difficulties as part of the process of spiritual growth and learning. They perceive problems as opportunities to enhance their own skills. As a result, they profit from even the most difficult challenges. Such people are practicing the paramita of diligence.