One of great writer once wrote. "It's only youngers who don't know how valuable to be young." = One of great writers once wrote, "it's only youngers who don't know how valuable to be young."

We can't assume all aged less happier than youngers. = We can't assume all aged less happier compare to when they were young.

It's over simplification. Nonetheless, it is beyond shadow of doubt that olders tend to less happier than youngers. = Nonetheless, it is beyond a shadow of a doubt that olders tend to be less happier than when they were young.

None of lucrative assets can be compared with youthfullness.

As time goes by, we gets wiser and get to know true value of being young. = As time goes by, we become wiser as we get to know the true value of being young.

And need more effort to be happy, after experience number of things in this world. = It needs more effort to be happy, after experiencing a number of things in this world.

So let us do away being idle. = Let us not be idle. / Let us keep ourselves away from idleness.

We need more effort to be happy as we get older.

Stop grumbling. Then your vitality eventually come back as were in youth. = Stop grumbling and then your vitality will eventually come back as were in youth.