Jesus says plainly: Unless you change and become like little children, you will never enter the kingdom of heaven — Matt. 18:3 NIV.
US researcher Robert Provine has found that kids laugh 300 times a day. It sounds to me like Jesus wants us to have more joy (I confess I myself am overly serious).
What’s surprising is that 1 Peter 2:2 exhorts Christians to “grow up” in their salvation. So it’s clear that Christian maturity involves becoming like children: they don’t harbor grudges, they love freely, they laugh.
Mustard Seed Budget 