Babies need a brake too.
Did you know babies need a brake from over stimulation? When your playing with them and they suddenly look away and start to fuss, that might mean they need a brake. I noticed my daughter after we do tummy time, reading and babbling to one another, she would start to fuss. So I would put her in her swing, or lay her down on her actviity mat and put some classical music on. A few minutes later she is happy and ready to play or eat again.