Life changes...roll with it

Older people seem to live calmly and happy and without a care in the world. Why is that?

They have gained enough experiences in life to cope with whatever comes at them. (for the most part)

We can only deal with things if we have a coping system in place to process the situation. The more experiences you have in life the stronger the coping methods you will devise on the fly. Sometimes you will have to work hard to figure out solutions to your problems. (solutions - coping methods)