Why have you chosen me?

This song is included in our church Caring Group Fellowship's worship song book, I found the lyrics of this song is really beautiful and so real...

Why have You chosen me out of millions Your child to be?
You know all the wrong that I've done
O how could You pardon me, forgive my iniquity
To save me, give Jesus Your Son

Reff:
But (Oh) Lord, help me be, what You want me to be,
Your words I will strive to obey;
My life I now give, For You I will live,
And walk by Your side All the way

I am amazed to know that a God so great could love me so
He's willing and wanting to bless;
His grace is so wonderful, His mercy's so bountiful
I can't understand it I confess