On his website, Arminian Perspectives, Ben Henshaw has a questions page at which he answers questions about Arminianism and Calvinism that visitors to his site pose in the comment section of the page. The following is a question and answer interaction between Ben and a commenter named William:
Question: What are your views as to when a person loses their salvation. There is that long list of things in Galatians which if you practice them you will not be saved. So how long does it take before you lose your salvation. How long can you get angry before you no longer are saved? I’m perplexed by this.
Answer: Not sure if I can give the solid answer you desire here, as the Bible probably doesn’t give a clear cut answer to this question. I think the first thing we need to do is recognize that Christians do struggle with sin. The key would be struggle (as in struggle against). As long as the believer is struggling against sin, though he may fail, he is living by faith. If a believer begins to not take sin seriously by not repenting of it when the Spirit convicts, or ceasing to struggle against it (by essentially giving in), then that person is not really living by faith, and would have good reason to question his salvation.
Sin leads to a heart that is hardened against God, but only if it is no longer resisted. The soul that continues to resist and battle sin, and call out to God for victory, is living by faith in (and love for) God. The soul that no longer resists and gives up the battle, is no longer living by faith in (and love for) God. Are we satisfied with our sin, or do we despise it and struggle against it? In the realm of continued sinning, I think that is the main difference between faith and unbelief. As we struggle against sin, we will slowly gain the victory, and our lives will be less and less characterized by sin and more and more characterized by holy living. A life of no change at all, likely reflects a life of no faith at all. Paul is giving an example of a life that is characterized by sin and unrepentance, a life that has fully surrendered to sin. Such a person will certainly be excluded from the kingdom of God.
The point of these warnings is to help believers to always take sin seriously and never become comfortable with sin in their lives. Ignoring the dangers of sin will allow sin to flourish and ultimately lead to a life surrendered to it (rather than God), and that is a life of unbelief, rather than faith.