It is troubling. It is the terrible problem of mortality. We are all prone to drift and fail. It is only by constant renewal of faith that we can hope to succeed. No matter how far we have come, what great things we have obtained, we are still subject to failure. This is why the FIRST principles and ordinances of the Gospel are: "faith, repentance, baptism and laying on of hands for the gift of the Holy Ghost." We never outgrow these FIRST principles.
I believe them to be "FIRST" in the sense of primacy, not a singular event which happens and then you can take them off the list of stuff to do. They are primary. They are foundational. They are required to be used constantly. Therefore, they are "FIRST."
So, we always go forward in faith. No matter how much we already know, we must use faith to go forward. We live within the limitation of linear time. We experience things in a flow that happens without our control. Life unfolds as an unknown to us, and we must cope with all it hands us from day to day. That requires faith to confront this uncontrolled, unfolding stream of time in which we are presently confined.
Repentance is required because even if we are doing what we should be doing we are always going to learn more. It is the nature of the Gospel that our light should increase. Whenever we learn more, we must change to reflect what we have just gained. Change is the heart of repentance.
Baptism is to have sins washed away. If you are already baptized, then the ordinance does not need to be done again, but the remission of sins and washing them away is required repeatedly. For those already baptized, this is done through the Sacrament. It is still required for us to have sins remitted.
The Holy Ghost is should be a regular participant in our lives. Its renewed companionship is also primary. Its witness to us that we are on the right path is the only way to wage the necessary war against entropy which seeks to take you into darkness. It is the source of renewed light that always enlightens when it comes.
These are the only means by which we can avoid the same dismal fate as all others of all prior dispensations. We must do this individually. It does not matter if it is done collectively. I've yet to see any reason in the scriptures to expect great collective success by the Gentiles who inherit the Gospel in our dispensation. There are individual promises to the few Gentiles who will repent, have faith, be baptized, enter into the covenant and remain faithful. But the collective outcome is not particularly rosy.