The Race is Won by Running (by ? )

The race is won by running -
There is no other way;
And if you keep on running,
You will win one day.

[Suppose you study music;
There is no other way-
You have to practice music;
Then you will play one day.]

[We may not think our schoolwork
Amusing as the rule
But there'd be no vacation,
If there were no school.]

[The race is won by running
It's fun I do declare
Just think what fun the tortoise had
The day he beat the hare.]

[...]

So dig right in and do it now -
Whatever should be done;
You're a dope to sit and mope
When everything is fun!