” You are like salt for the whole human race; but if salt losses its saltiness: there is no way to make it salty again. It has become worthless, so it is thrown out and people trample on it.” (Mathew 5:13)
When you give your life to christ, you become a new creature. (2 corinthians 5:17) The old is gone and the new has come. There are things that you did while in the world that you no longer do. Your way of thinking, and of acting completely changes in line with your new nature. Even your entourage would realise you have changed for the better in so many ways.
What makes you the salt on earth? It is the good deeds that you do. You no longer womanize, prostitute, lie, smoke nor drink beer. You pay your thithes and offering in church and you become an addicted giver. Anybody looking at you knows you are a child of the most high God by the way you behave. How then do you loss your saltiness? You loss your saltiness when you start doing those things you were doing while in the world. If people see you womanising, drinking beer in an off license, lying then you can no longer be identified as a child of God because your deeds do not show it.
This scripture simply tells us that when you are devoid of those good deeds you lose your holiness. You are no longer a candidate of heaven. You have lost the substance of what makes you a child of God.
When you realise you are in this situation, run to God not away from him. He is more than ready to forgive your sins and welcome you back into the kingdom.