I guess I don’t understand. If Christ doesn’t need our help to save souls (which I believe he doesn’t) why would he allow us to help? The very idea that I, a sinner, can help save someone’s soul sounds just so self-important. I am not a savior. I am not even a “partial savior”…I am a woman in need of a savior as is every other person who has walked this earth other than Christ. He doesn’t need our help. If he has done it (past tense) once and for all for us, how and why could we save people’s souls as mere humans? It just doesn’t make sense to me.
PhilotheaZ gave an excellent example here - the child helping the mother make dinner.
God wants to involve us in His plan of salvation. Does he have to? No. But it was the sin of Adam & Eve that caused the fall of man, and so God chooses, in His mercy, to permit man to play a part in his own redemption. No sacrifice that we make is alone sufficient to save a soul, but when united to the cross of Christ, our sacrifices do, in fact, gain us merit. Again, please refer to CCC 2006-2011 for more on this. This is the official teaching of the Church.
Let’s turn back to the PhilotheaZ’s example. Little Danny is 6 years old and his mom is in the kitchen preparing the family dinner. She is fully competent to make the dinner herself and she requires not help of any kind, but Danny comes in and asks if he can help. What should Danny’s mom do? Send him away saying, “I can do this on my own, thanks very much?” No, of course not. Assuming that it is safe to do so, she will allow Danny to help. Perhaps he can help her beat an egg, stir a pot, pour some carrots into a salad bowl, or anything else.
This story is analogous to our role in our own salvation. Yes, the Sacrifice of Jesus is sufficient for our salvation, but it is in God’s divine plan that we should play a role, as well. And in His mercy, God has allowed that our sacrifices and our merits can aid in the salvation of not only our own soul, but also the souls of others.
Why does God allow this? Why does Danny’s mom allow him to help her? Because she loves him and she wants to see him grow. By giving us the opportunity to unite ourselves to the sacrifice of Christ, God gives us the opportunity to grow.