Heart beats!
Its function is to expand and contract.
This opening and closing, means expansion and contraction , is perceived as a beat.
Beat signifies life.
Beat gone , means life is gone.
Heart rests when life is to rest, that is death.
But this is not true in an absolute sense.
There is a pause intervening between each successive beat.
The impercptible time lag between beats is ,in fact, a pause that the heart uses as its relaxation moment.
So we are told, slower the heart beat, the better, which is an involuntary function, it depends on the load it carries, in a relaxed state, hear beats get slower and so does the breating rate.
Focusing the mind on the pause that occurs continually is a meditation form which slows down the pulse. Likewise, there occurs pause on to points of breating, one at the end and the other at the outset of each inhalation or exhalation. To become aware of both, or even either, leads to the lengthening of the above said imperceptible pauses in the heart beats or breathing, calming down the mind.
The above breathing and pulsating mechanisms carry a moral too fir the human kind.
It predicates, never to feign excuses under pretext of being busy elsewhere, for your heart and breathing are both intelligent mechanisms. What if, either some day take similar excuse why it stopped for greater moment than survival unavoidably requires?