11 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.12 And he hath risen again from the dead, that he might bring all men unto him, on conditions of repentance.
13 And how great is his joy in the soul that repenteth!
I love how this section of the D&C so explicitly links our obligation to do missionary work to the love that God and the savior has for us. In particular, these verses contextualize missionary work in light of the atonement. Christ gave up so much for us and he is overjoyed when we repent and come to him. His love is the primary consideration motivating his service. Likewise, we must be motivated to act out of love and out of appreciation for the abundant blessings of the atonement. If we serve with that framework in mind, then we will be effective in preaching the Gospel even if we labor all our days and see little to no success.