Humility is the realisation and internalization of the limited natur of our existence.
In order to achieve a correct measure of humility, one needs to have a realistic understanding of the nature of the universe and themselves, leading to a correct estimate of their relation. And in order to do that, the person is required to be sane. As much as the person is realistic in their worldview, the more they will be able to avoid undue grandiosity, the opposite of humility. And that in turn will enable the person to emotionally appreciate realty in a healthy way.
Being unable to maintain a healthy humbleness will damage both the prerequisites of humility and what is enabled by humility. Thus, a lack of humility will encourage a deterioration of both mental sanity and emotional health.
Humility in different fields
Influence on divinity
Realizing that there are things outside of one creates the need to have a stance towards that which is outside. Managing to see width and depth of reality creates awe and devotion for it.