Calvinism's mistaken doctrine of once-saved-always-saved through assured perseverance unwittingly ends up logically requiring that saved people are robots. For if saved people cannot choose to do evil to the point where they can ultimately lose their salvation, then they no longer have free will. Also, the mistaken doctrine of assured perseverance unwittingly ends up logically requiring that a Christian can have no present assurance that he is truly saved. For if a Christian who does not persevere to the end was never truly saved, then no Christian can presently have the assurance that he is truly saved. For no Christian can know if he will persevere to the end. Down the road, he could fail to persevere, and so end up showing that he was all along only a fake Christian, a self-deceived hypocrite.
But under true, Biblical doctrine, every believer in the gospel (of 1 Corinthians 15:1-4, John 20:31) can know that he is presently saved (1 John 5:13; 1 Corinthians 15:1-4), if after he became a believer in the gospel he repented from his sins (1 John 3:6) and confessed them to God (1 John 1:9). And he can be sure that as a saved person, he can never be separated from the love of God, so long as he loves God (Romans 8:28-39), which means to obey him (1 John 5:3, John 14:21-24). And no matter how many tests a saved person fails during his lifetime, sometime subsequent to his initial repentance, even if he fails and commits sin 70 times 7 times in a single day (Matthew 18:21-22, Luke 17:4), he can be sure that so long as he sincerely repents from every act of sin and confesses it to God, he will be completely forgiven (1 John 1:9). He will lose his salvation ultimately only if he wrongly employs his free will to do something like committing a sin without repentance (Hebrews 10:26-29; 1 Corinthians 9:27, Luke 12:45-46), or becoming utterly lazy without repentance (Matthew 25:26,30, John 15:2a, Romans 2:6-8), or committing apostasy (Hebrews 6:4-8, John 15:6; 2 Timothy 2:12).