Perfect Peace

“Thou wilt keep in perfect peace the mind stayed on thee, for he confideth in thee” (Isaiah 26:3, J.N. Darby trans.).
Do we believe and prove the above words of God? Though oppressed and surrounded with difficulties, can we know this “perfect peace” of heart and mind? Is it a practical, absolute defence for us in every circumstance and trial of life, or should we consider it an impossibility?
https://plymouthbrethren.org/article/9659