CAN SALVATION... ONCE GAINED...BE LOST?

It would be profitable to first attempt an understanding of that which is to be "lost."

First, consider all that God did to make His salvation available to you. This was not some "patchwork" solution to a problem which He had not foreseen. Rather, before His act of creation, His plans had been laid:

According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
Ephesians 1:4