I believe that the Bible is God's inspired word, and is inerrant. Since God does not need the Bible Himself, I assume that He wrote it for the benefit of others, namely humans. Of those humans, the Bible says that to the lost the teachings of the Bible are nonsense, and are therefore of no use. So, I conclude that the Bible was written for the benefit of Christians.
This means that everything in the Bible applies to me (at the very least for educational purposes), if I am a Christian. I first know I am a Christian because God has given me the faith to know it. What is faith if a Christian cannot know he is a Christian? More objectively, the Bible describes in very great detail what a Christian looks like, what he believes, how he thinks, what he does, and says. Upon self-examination, I am satisfied that I look very much like a Christian, including the fact that I still sin.
Now, if I may have certainty that I am a Christian, and if I may also know that the Bible was written for my benefit, then I think it is fair for me to believe that the assurance verses apply to me. They were not written for the benefit of the reprobate, they were written for the benefit of us. So, I simply accept them with all the thanks I can muster in gratitude to God. He didn't have to give them to us, but He chose to. Praise God for it. Besides, of what value to any Christian are those verses if no one can know if they mean anything for him personally? Why did God include them?
That seems rather circular. (Maybe Gamecock will bless us with his colorful illustration.) The assurance verses apply to you, because you are not reprobate; your certainty that you are not reprobate lies in the assurance verses.
The assurance verses apply to the elect of God. You cannot infallibly know you are among the elect of God until you know that you have the grace of final perseverance; you cannot (without a special revelation) infallibly know that until it happens. (I say "infallibly" because you can certainly have a moral assurance or certitude sustained by the virtue of hope.)
But all those Christians who later apostasize think they know that they have faith when in fact they do not really know that they have faith. So how do you know you are not one of those people who thinks he knows that he has faith when in fact he does not really know that he has faith? In other words, how do you know that you are not an apostate-to-be? (Appealing to the 'assurance verses' here would simply beg the question, because it would assume precisely what you are trying to prove, namely, that the 'assurance verses' apply to you.)