Steadiness
Isaiah 26:3
Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.
“Stayed” is an old word for propped, braced, held in place. It is what you do with a ladder before you climb it. This is not describing a calm mind. It is describing a mind that has been leaned against something.
Which means the peace here is not the starting condition. It is downstream of where attention is resting, and attention moves. That is why it reads as a promise rather than a description: it tells you what follows, not what you will feel on the way there.
“Perfect” in older English means complete rather than flawless. Nothing missing from it. Not nothing wrong around it.