After struggling with insomnia for all my adult life, I can tell you with great confidence that there are many different reasons why someone may struggle to sleep. Rest, with which sleep overlaps so much, is obviously the same.
Just as the shepherd calls the sheepdog away so the sheep can settle, resting requires us to safeguard ourselves – for a while and as best we can – from those things which conspire to keep us constantly in physical, mental or spiritual motion.
Many of those things are largely within our control. We can work at eating more healthily and exercising more wisely. We can cultivate better attitudes towards our phones and our to-do lists so that we aren't constantly driven to give either or both of them our attention. And we can establish better routines which enable us to spend more concentrated time with the Lord and with our families and friends. These are all changes which we can begin making today. All of them will play a part in improving our rest.