This amazes me every time I read it. Peter was ASLEEP in prison, in chains, and who knows what else was happening below human dignity, but that dear Saint of GOD was asleep! He had certainly given all his cares to the Father.  Perhaps that is why he could pen for us in 1 Peter 5:7 to cast all our cares on Him, for He cares for us. 
There’s more to unpack in this verse. What do you see? 

Holy hugs, Kathie