2 Nephi 25:26 And we talk of Christ, we rejoice in Christ, we preach of Christ, we prophesy of Christ, and we write according to our prophecies, that our children may know to what source they may look for a remission of their sins.
I think it's interesting that Nephi doesn't say that they preach of Christ so that their children will turn out perfectly, or have perfect testimonies.
Instead, he says that they, the prophets, write to make sure their children know where to look when they need to be forgiven of their sins.
It makes me think of Alma the Younger. When he was 'harrowed up' by the memory of his sins, he suddenly remembered that his father had taught about 'one Jesus Christ.' His mind focused on this, and he turned to Jesus Christ and prayed to be forgiven.
This shows me that, once again, making mistakes, big ones and little ones, is a part of the plan. So when people that we love make mistakes, I guess it shouldn't surprise us. All individuals are given their free agency and the ability to learn for themselves right from wrong. This leads to mistakes, which are naturally part of the learning process.
Our job is t0 keep rejoicing in and preaching Christ to help those we love (and ourselves!) remember that we can turn to Him.
And sometimes the way we rejoice in and preach Christ is very quiet--by loving unconditionally.