After tasting salt and enjoying it without conscious thought of its presence. Salt also is a preservative. In the time before refrigeration, it was used on meats and fish to slow or stop the rotting or degradation process. In this way, Christ's presence in this world stops the degradation of the world. To add Salt to this world also has a healing affect.
Salt also stings when it touches bare flesh.
This is a reminder of those who do not know of the healing power of God. Upon first exposure to Him and His word, it stings the flesh, but also heals it. And this is unfortunate that those who first hear, tend to pull back, rather than allowing a full curing and preservation to take place. In many ways salt used in the wrong measure can cause a meal to be too strong to be palatable and If used too sparingly, then one cannot detect its presence. But, we should always leave ourselves open to the Spirit of God to guide us to show ourselves to the world.