According to Reformed Theology, What is the greatest assurance of Salvation? Context

Matthew 7:21-23


  Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.


James 2:14-16


  What does it profit, my brethren, if someone says he has faith but does not have works? Can faith save him? If a brother or sister is naked and destitute of daily food, and one of you says to them, "Depart in peace, be warmed and filled," but you do not give them the things which are needed for the body, what does it profit? Thus also faith by itself, if it does not have works, is dead. But someone will say, "You have faith, and I have works." Show me your faith without your works, and I will show you my faith by my works. You believe that there is one God. You do well. Even the demons believe—and tremble! But do you want to know, O foolish man, that faith without works is dead? Was not Abraham our father justified by works when he offered Isaac his son on the altar? Do you see that faith was working together with his works, and by works faith was made perfect? And the Scripture was fulfilled which says, "Abraham believed God, and it was accounted to him for righteousness." And he was called the friend of God. You see then that a man is justified by works, and not by faith only. Likewise, was not Rahab the harlot also justified by works when she received the messengers and sent them out another way? For as the body without the spirit is dead, so faith without works is dead also.


1 Corinthians 13:2


  If I have the gift of prophecy and can fathom all mysteries and all knowledge, and if I have a faith that can move mountains, but do not have love, I am nothing.


John 14:23-24


  Jesus answered and said unto him, If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him. He that loveth me not keepeth not my sayings: and the word which ye hear is not mine, but the Father's which sent me.


Question

Thus, is the greatest assurance of salvation following the words of Christ? In that -- the teachings of Christ are so impossibly hard to follow for the non-believer that only the true believer can follow them?
This response is inspired by:
http://www.gty.org/resources/sermons/90-446/a-tale-of-two-sorrows

Let us compare the cases of Judas and Peter.

What can we learn?


Spiritual knowledge is not assurance of salvation. Judas likely knew more about Christ than many of the future great theologians, yet Judas fell away.
Signs is not assurance of salvation. Judas witnessed some of the greatest signs of all time, yet Judas fell away.
Discipleship + being in the right church is not assurance of salvation. Judas hung out with Christ and the 11 true disciples.


So then, what is the assurance of salvation? It's likely the love of Christ vs the love of the things that Christ can provide in this world. Peter loved Christ: John 21:15-17. Judas appeared to love what Christ could provide in this world (and thus betrayed him upon realization that the earthly kingdom would not be immediately established.)

Then, this love is manifested as in John 14:15.