There are too many scriptures that indicates that "once saved, always saved no matter what" is not Bible.
I'll share just one set of scriptures here:
Our names are added to the "book of life" when we are genuinely born again according to scripture, the scripture below shows that your name could be blotted back out if you are not an overcomer.
Revelation 3:5 "He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life...."
.......and the following verse shows the consequences of not having your name in the book of life:
Revelation 20:15 And whosoever was not found written in the book of life was cast into the lake of fire.
(I am not saying it is easy to lose your salvation at the drop of a hat so to speak, but I would not want anyone to have a false assurance that they could backslide and still make Heaven if they did not repent and return to God before leaving this life)