To a six year old, on his birthday

My boy -
This morning I watched you run to class.
Feet tripping over each other,
Backpack bouncing awkwardly,
turning every few urgent steps
to wave goodbye,
your words carried off by the wind.

Tomorrow you'll be six.
The years rush by
faster than your rushing feet.
And I lose my breath,
winded by the realisation
that this goodbye
is just a practice run.