Remember the worth of souls is great in the sight of God; For, behold, the Lord your Redeemer suffered death in the flesh; wherefore he suffered the pain of all men, that all men might repent and come unto him. And he hath risen again from the dead that he might bring all men unto him, on conditions of repentance. And how great is his joy in the soul that repenteth! Wherefore, you are called to cry repentance until this people. And if it so be that you should labor all your days in crying repentance until this people, and bring, save it be one soul unto me, how great shall be your joy with him in the kingdom of my Father! And now, if your joy will be great with one soul that you have brought unto me into the kingdom of my Father, how great will be your joy if you should bring many souls unto me!
Doctrine and Covenants 18:10-16
I like to think that the first soul, or that one soul, we bring to God is our own. We still spend our days sharing the Gospel with others, but the biggest difference will be made in our own life.