Jesus was sleeping at the back of the boat with his head on a cushion. Mark 4:38a NLT
After completing a full day of teaching, Jesus was exhausted. He instructed the disciples to get into a boat and go over to the other side. He went into the stern and fell sound asleep on a cushion.
A fierce storm arose, water was cascading into the boat, and the disciples feared for their lives. None of this bothered Jesus because he was at peace with the wind and the waves. After all, wasn't he their master?
Jesus needed rest from his labors, and so do we. We can push our bodies just so far before fatigue sets in and the body functions shut down. Peter, James, and John experienced this when they fell asleep from exhaustion in the Garden of Gethsemane. Soldiers know this when they have to stay on alert for forty-eight or seventy-two hours. They suffer what is called "battle fatigue." R & R is necessary for the body and mind to stay fresh and alert.
I have found that it is much easier to gain a sound sleep when all is well between my and the Savior. I can have the "peace of God that surpasses all comprehension" that Paul talks about in Philippians 4:8.
Ask yourself, "Do I have peace with God?" If you do, then the peace of God is available to you.