I have found this verse to be abundantly true, but the trick is keeping my mind stayed on God. I am distracted by all sorts of shiny objects, grandiose visions, trials and tribulations, headlines, and headaches.
Personally, getting closer to the restful ideal described by Isaiah involves turning my thoughts to God in ACTIVE TRUST, many times a day (or an hour), if only for a few moments. I often say out loud, “I trust you, God” or “Thy will not mine be done,” or "Please redirect my thinking."
It’s like that old ditty, “Don’t tell God how big your problems are. Tell your problems, how big your God is.” Amen.
This is surely as or evermore important when things are going very well, which can also derail us in a big way, taking our eyes off of God. Perilous waters anyway you slice it.