I think there is a misconceptions going around about the once saved always saved doctrine.

If anyone goes out and starts living whatever life they please, then they were never saved. For if they had been saved they never would have returned to their old life style, rejecting the cross.

When a person is truly born again their hearts and minds change. I've seen this many many times. Complete turn abouts from what they used to be. Not because they have to, but because Jesus is in them.