To rephrase the hymn writer’s lyrics:

If we had confidence in our own strength,
our efforts would be a lost cause;
If the right Man wasn’t on our side,
The Man of God’s own choosing.

Because Christ Jesus is on our side, we know that our striving is not in vain. It is no longer futile to strive after righteousness now that we live as those whom He has adopted. It is finally possible to live before God and to please Him with righteous works lived out in this world.