From the time a person accept Jesus Christ as their personal savior, they become a new creation in Christ according to the apostle Paul. Yes, the old is gone, and the new has come. This is true of the experience of every Christian and from there on it is a struggle to finish the race that they have begun.
It is also a time when you realize that in being a Christian, this is the only way by which you can truly prepare for death when you will face God on the Day of Judgment.
Yet there are so many Christians, despite knowing what the repercussions of straying are, tend to be swayed by doctrines and teachings made by men who have twisted the Bible for their own purposes. Yes, Jesus called them ‘false prophets’ and perhaps one of the biggest examples of this is the 5 points of Calvinism which support the claim that salvation is only for a chosen few, even if they do not want it.
These are teachings that will only lead you back to the old ways of living, and this is something that should be avoided especially if you have begun to believe that eternal security is your birthright from the time you accepted the Lord Jesus into your heart.
If you do doubt these doctrines, one way by which you will know whether or not they are true or false is by checking the Word of God for scripture verses that support or refute these teachings.
If you want to remain a new creation, then this is something that you cannot simply ignore, for on the Day of Judgment you will find yourself with no answers that will satisfy God let alone yourself.