We all know such persons. How do they manage it?
Just by prayer, that is all. Those persons who know the deep peace of God, the unfathomable peace that passeth all understanding, are always men and women of much prayer.
Some of us let the hurry of our lives crowd prayer out, and what a waste of time and energy and nerve force there is by the constant worry! One night of prayer will save us from many nights of insomnia. Time spent in prayer is not wasted, but time invested at big interest.
R. A. Torrey, How to Pray, Olive Tree Bible Software Edition