There are endless variations of belief on freewill vs predestination, but I'll leave those weeds for the theologians to explore. In general: you have Arminianism, which teaches that humanity is depraved, but not to the point that we can't use our own freewill to choose God. In turn, being omniscient, God can look forward and know who will choose Him and who will reject Him, with the former becoming His 'elect' and being rewarded with eternal life. In this school of thought, because of his freewill, which God won't violate, a person can fall away and ultimately lose salvation. Then you have what is referred to as Calvinism (though these beliefs certainly predate John Calvin,) which teaches that: courtesy of original sin, all humans are totally depraved, dead in sin, and unable to use their freewill to choose God. Instead, God is sovereign in the entire process, giving His elect the ability to choose Him; God first chooses us, so that we may be empowered to ultimately...

  This sounds absolutely awful, I know, but it’s the truth. To clarify though, first let me describe what I’m not saying: since we can’t possibly live up to God’s perfect moral standards, we should just throw in the towel and quit trying. Since we aren’t ever going to be good enough anyway, why not go all-in on sin, and enjoy the ride? This would be a very easy way to justify the sinning that we all love so much, but would obviously be a very self-defeating moral philosophy. No, instead what I’m saying is that in the eyes of a Holy God, fallen sinners will never, can never, please Him. We humans love to believe that we are ‘generally good’ – and we may well be – when judging by low human standards. But we can’t compare human standards to God’s standards. As an example: suppose a person spent every day of his life, from morning ‘til night, helping little old ladies across the street. By human standards, this person would be described as ‘saintly’ and ‘selfless’, and there would b...