Who is this following me?

When I go out on sunny days,
there is something right beside me:
And there it skips and there it plays,
And from it I can't hide me.
I cannot run away from it,
It runs as fast as I do;
And if I stand or if I sit
It stands and sits as I do.

Kendry is fascinated by his shadow….he watches as he walks and it walks beside him.