"Verily, verily, I say unto you, I give unto you to be the salt of the earth; but if the salt shall lose its savor wherewith shall the earth be salted? The salt shall be thenceforth good for nothing, but to be cast out and to be trodden under foot of men."
Salt is a preservative, but in this case it is for the culinary benefit. It produces "savor." That is, the taste of the whole is affected by the presence of a little.
You don't need much to preserve the whole. Abraham's negotiation to preserve Sodom demonstrated that only a little of the "salt" is required for an entire population to receive the Lord's blessings. (Genesis 18: 17-33.) Progress is enough in our day. (Luke 13: 30.) As long as the wheat is still growing, it is enough.
How can salt "lose its savor" except through contamination or impurities? When that is lost, the salt cannot preserve. There is no remaining savor. Then the salt is nothing more than common dirt, to be cast aside and trodden under foot.
This is the gentile predicament in the last days. They will, of course, lose their savor. They will reject the fullness offered to them. (3 Nephi 16: 10.) When they do, they will be torn apart and trodden under foot. (3 Nephi 20: 16; 3 Nephi 21: 12.)
Notice it is the Lord who "gives unto you to be the salt of the earth." This condition is a gift from God. Through repentance, or turning to Him, you can receive this. Without repentance you cannot become the salt.
There are no private lives. Every life counts. Your private devotions are more important than your public notice. The salt which preserves may be unknown, likely is unknown, to most people. But if you are the salt, then your private life of devotion to the Lord is saving the lives of many others. The angels want to begin the harvest. They are impatient to begin reaping and cutting down the wicked now. (D&C 86: 5.) There is only time given because of a few who deserve more time to grow in faith before the harvest begins. (D&C 86: 6-7.) Your growth is all that is keeping the harvest from beginning now. Therefore, how you proceed has consequences far beyond your own life.
When wheat is ripe it will be protected. When tares are ripe they will be burned. But the tender plants worthy of preservation are the only ones allowed more time. (D&C 86: 4.) I advocate for them and realize how tenuous a position humanity itself is in at present. But you are the ones in the balance and for whom time is granted. How much longer no one knows, but your sins are not private. Your repentance is critical to all of creation. Do not think your life is your own. All of us have a share in your good works.
Do not think the Savior's words are without cosmic significance. I define "cosmic" to include the cosmos or organized creation here. Even the earth itself longs to be freed from the burden of sin upon her face. (Moses 7: 48.) It is the Lord alone who has granted you time to repent. This current state of the creation we live is affected by the promise held in those who are repenting. As soon as that hope ends, and no further repentance is to occur, then the harvest will begin. Therefore, becoming salt has never been so important as it now is.