We are living in a time where being overworked is considered a badge of honor. We neglect our families, other things that bring us enjoyment, and our own well being. This is not healthy and God shows us that.
When God was creating the world, He found it important to take a day of rest from His work. If rest was important to God, what makes us think that we don't need it? One thing that God has shown us through history though is either we can start taking this seriously and take necessary rest for ourselves, or God will force us to rest.