The power of laugh

When people become mature, usually they forget how to laugh.
In other words, it's more difficult to feel things arounds you interesting.
Is that because we are more greedy, not satisified easily, or just not like a child anymore?

Laugh really heal , withought doubt.
One research before shows that although you make a laugh on purpose, this "fake" laugh still can make you happier.

I know we're already adult; however, sometimes how about just pretend we were still children so that could laugh without any specific reason. I can't order my life, but I can decide which way I'd like to live my own life - happier views sounds like a sensible choice.