The deep, forceful chest movement in itself sets the blood to racing thereby livening up the circulation--which is good for us.

Perhaps you hadn't thought of that?
Perhaps you didn't realize that laughing automatically re-oxygenates the blood--_your_ blood--and keeps it red?
It does all of that, and besides, it relieves the tension from your brain.
_Laughter is more or less a habit._ To some it comes only with practice.
But what's to hinder practising?
Laugh and live long--if you had a thought of dying--laugh and grow well--if you're sick and despondent--laugh and grow fat--if your tendency is towards the lean and cadaverous--laugh and succeed--if you're glum and "unlucky"-- laugh and nothing can faze you--not even the Grim Reaper--for the man who has laughed his way through life has nothing to fear of the future.

His conscience is clear.
Wherein lies this magic of laughter?
For magic it is--a something that manufactures a state of felicity out of any condition.

We've got to admit its charm; automatically and inevitably a laugh cheers us up.

If we are bored--nothing to do--just laugh--that's something to do, for laughter is synonymous with action, and action dispels gloom, care, trouble, worry and all else of the same ilk.
Real laughter is spontaneous.