Our Scripture reading today is Isaiah 26:1-5.
Verse 3, "Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee."
The key to obtaining perfect peace is where are we placing our trust.  We can find ourselves fretting and worrying at circumstances that are completely out of our control.  When this is taking place, we are not anchoring our trust in the Lord.  At this point, our trust is in ourselves or someone else.  We are admonished in Proverbs 3:5 not to lean on our own understanding.  This type of thinking is what leads to worry and fear.
The prophet Isaiah makes it very clear how we can have perfect peace all of the time.    Our trust and confidence is to be placed in the One Who has never failed and is not about to start failing with you or me.  Our heavenly father has a perfect record.  He faithfully provides us with a peace that goes beyond our understanding.  He is with us in the valley and on the mountain.  We can lean ("stayed") on Him and know that His will is always best.
Have a wonderful day!