Constant Beating

Constant beating of my heart
please keep beating. Don't depart.
You keep me going all day long
able to hum a happy song.

I never stop and ask you why
I don't have to make you try
to beat for me. You just do.
How you do that, I've no clue.

Someday when you're all worn out
I will wonder all about
how you kept me going so long
so I could hum my happy song.