Yes, it is possible for a man to deceive himself, either side, and your super abilites of free will in a fallen state give you no leg up in this department. So tell all of us, how does this ability to choose the Lord tell you that you have eternal life? What told you, since you like to make fun of people who use the word realize? Was it an email from above, or maybe your aura lit up a bright white when the Lord jumped for joy that you chose Him?
There seems to be another super human ability you have. It seems from your posts you can look into the very soul of another and see whether they are saved or not. Otherwise, how do you know that people who use the word "realized" are deceived. I wish you would teach me that trick.
You harp on "Calvinists" for the fact they have nothing to base their salvation on, yet you fail to tell us what you base yours on. If you had bothered to read the Scriptures, you would know that the Holy Spirit bears witness to our spirit that we are saved, regardless of which side you take on this issue.
I will be glad to explain my super-abilities (that was sarcasm).
I know I am saved because the scriptures say so. It is not because I got some feeling, or came to some realization.
The scriptures say if a man believes on Jesus Christ he will be saved. To believe on Jesus Christ you must understand what "believe on" means. It means to depend upon, trust, rely upon, or cast yourself upon Jesus and depend upon him only to save you. It is a committment. I have explained this in many posts. I have written several posts telling how a person can know from scriptures if they are saved.
The scriptures provide many verses that explain this in different ways so as to make it clear that every person can understand. For brevity I will just show two.
Rom 10:13 For whosoever shall call upon the name of the Lord shall be saved.
The scriptures say whosoever shall call upon the name of the Lord shall be saved. That is very easy to understand, a child can understand that. This means if a man will accept the truth of the scriptures that he is a sinner worthy of death, and believe that Jesus Christ is the Son of God who died for his sins and rose from the dead, and call upon Jesus for forgiveness, which is an act of dependence and trust, he will be saved.
Now, I know for a fact that as an eleven year old boy I understood all this. And I got down on my knees and sincerely prayed and asked Jesus to save me. I don't have to wonder about this, I don't have to come to some realization, I know I did this. And I meant it with all my heart. So, I know by the word of God I am saved. God does not lie.
Now, on the other hand, I can see where this would not be assuring to a Calvinist, because they do not believe "whosoever" means "whosoever". They believe whosoever only means an elect few.
So, how can a Calvinist have assurance? They don't believe God means whosoever when he said whosoever. That is your problem, not mine.
Rev 3:20 Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.
This is a salvation verse, although I have seen many Calvinists say it is not. Again, your problem, not mine. Here Jesus says he is knocking on your door. He is calling to you. And if you open the door he will come in. This is speaking of a man's free will. If a man of his own free will invites Jesus into his heart, Jesus will come in and he will be saved.
And again, I know I did that. I don't have to wonder or come to a realization that I invited Jesus into my heart and asked him to save me. I know for a fact that I did that. And so I know by the solemn promise that Jesus gave in his word that I am saved and he lives in my heart.
Again, this is a problem for Calvinists. This verse if offensive to them for several reasons. First, they do not believe an unsaved man has a free will. They do not believe an unsaved man can decide for and choose Christ. And even if they could, Calvinists think faith is a work. They cannot allow that a man do anything or participate in his salvation. They can't open the door because they believe that robs God's sovereignty even though Jesus himself said you personally have to open the door. He won't break it down or enter without your permission.
And because Calvinists will not accept these easily understood verses that explain what faith is and how a person can be saved, they don't know they are saved. I will show an example.
Here is how one Calvinist explained his conversion
One morning, to make a long story short, I was suddenly and very surprisingly born again. Without praying a prayer, asking Jesus into my heart, et. I was suddenly filled with the Holy Spirit from above. The sensation of it was of total love, joy, and peace. Immediately my soul recognized that this was the Almight God, Maker of Heaven and Earth, touching...but I realized I did not know Him.
Now, I am not saying this person is not saved, I sincerely hope they are. But what is the basis stated here for assurance? A feeling or sensation. That is what this person is saying told them they were saved. They felt a sensation of total love, joy, and peace.
Now all that is wonderful, but I have learned long ago not to trust feelings. Feelings come and go. Feelings aren't the truth. If your teenager is late getting home with the car, you get all afraid worrying they were in an accident. You can get all worked up in a frenzy worrying. But whether you are afraid or not has nothing to do with the truth. Ten minutes later they walk in and you scream at them "Why are you late! You had me terrified, I thought you got killed in an accident!"
No, feelings are not a good basis to know you are saved. Today, if you feel good you believe yourself saved. Tomorrow if you feel bad you worry you are lost.
But when you trust the word of God and take them literally as they were meant to be understood, then you can know for a fact you are saved.