A creeping sense of finitude is ever persistent when you have a child. Particularly, in the first few weeks when you lose complete sense of time.
I have been reading Donald Hall's essays after eighty and carnival of losses. A deeply personal reflections of a poet when he is in his 80s and 90s.
I came across this poem of his from when he was lot younger.
My son, my executioner,
   I take you in my arms,
Quiet and small and just astir
And whom my body warms.
Sweet death, small son, our instrument
   Of immortality,
Your cries and hunger document
Our bodily decay.
We twenty-five and twenty-two
   Who seemed to live forever
Observe enduring life in you
And start to die together.