This may sound silly, but babies don’t know how to relax.  Just like most everything else it has to be taught to them.

This is be very helpful once your baby is ready to stop taking naps, but still needs that time just to unwind for a while to regain some energy.  This will also help your child be less cranky throughout the day, serving much of the same purpose as a nap would.

Encourage your child to relax with you, and this way your child will understand what it means to relax.  It could be sitting or laying together on the couch, or even just sitting out on some lawn chairs reading books.  Whatever it is that helps you relax, pass that on to your children.