how long can you stare at the unveiled sun?
“If, at mid-day, we either look down to the ground, or on the surrounding objects which lie open to our view, we [will] think ourselves endued with a very strong and piercing eyesight; but when we look up to the sun, and gaze at it unveiled, [our] sight, which did excellently well for [viewing] the earth, is instantly…dazzled and confounded by [the sun's] refulgence, as to oblige us to confess that our acuteness in discerning [earthly] objects is mere dimness when applied to the sun.
[So it is when] estimating our spiritual qualities. So long as we do not look beyond the earth, we are quite pleased with our own righteousness, wisdom, and virtue; [and] we address ourselves in the most flattering terms, and [even] seem only less that demigods. But should we once begin to raise our thoughts [toward] God, and reflect [upon] what kind of being he is, and how absolute the perfection of [his] righteousness, and wisdom, and virtue, [which of course is the standard to which we must conform], [then] what formerly delighted us [in ourselves] by its false show of righteousness will become polluted with the greatest iniquity…”
-John Calvin Institutes of the Christian Religion, Book First, Chapter 1, Section 2