Guài means firmly resolute. Line five, with yang firmness and the body of The Creative, occupies the supreme position, relying on its firm resolution in action. If one acts like this, even if one attains correctness, it remains perilous and severe.
When ancient sages occupied the supreme station of the realm, their discernment was bright enough to illuminate all, their firmness strong enough to decide all, and their authority sufficient to rule alone; yet they never failed to exhaust the counsel of all under heaven, even adopting the words of lowly grass-cutters—this was precisely what made them sages.
Treading the imperial throne, his virtue should be glorious and bright. If one relies entirely on one's own firmness and clarity, acting decisively without regard for others, even if one attains correctness, it is still a perilous path. Can this be steadfastly held?
Even one with firm and brilliant talent who acts with solitary self-reliance walks a dangerous path; how much more so one whose firmness and brilliance are deficient!
In The Changes, the meanings of "perseverance brings danger" differ across contexts, as seen in each respective hexagram. The Xiang says: "Resolute treading; perseverance brings danger": the position is correct and appropriate.
The admonition against resolute treading is because he occupies the honored position.
Dwelling in the supreme position and possessing the power to act autonomously, if he relies on his own decisive firmness without further fear or caution, even if he attains correctness, it is still a perilous path.