I read about the 14 steps of losing your salvation and I totally agree, but one of the arguments some Christians have is, What about your free will? Can you give the free gift of salvation back once have received it from God by announcing that you don't believe and want it anymore?  Will God accept his free gift back? Is our Free Will so strong and powerful, that God has to honour it?

I fear that in a desire to avoid the fatalism of strict Calvinism (something Calvinists would deny), many have gone to the other extreme. I have begun to hear "free will" being proposed as one of the unquestionable truths that must be accepted when it is applied to a discussion no matter how ridiculous the outcome. [Please understand, I am not personally accusing you of this.] However, the Bible does not seem to give the authority to "free will" that many do today. Just for instance, consider these three scriptures:

1. Matthew 26:41Watch and pray, that ye enter not into temptation: the spirit indeed is willing, but the flesh is weak.
   See All... Watch and pray, that ye enter not into temptation: the spirit indeed is willing, but the flesh is weak.
2. Romans 7:18For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
   See All... For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
3. Philippians 2:13Behold, is it not of the LORD of hosts that the people shall labour in the very fire, and the people shall weary themselves for very vanity?
   See All... For it is God which worketh in you both to will and to do of his good pleasure.

In the first two references, we see that whatever the operation of the will is, it is not able to perform what it wishes to do. So, although the will may have a freedom to desire a certain action, it does not have the power to perform the desired action without the help of the Lord. In the last reference (Philippians 2:13Behold, is it not of the LORD of hosts that the people shall labour in the very fire, and the people shall weary themselves for very vanity?
See All...), we see that both the willing and the doing of the right thing comes from God. Yet, I sense that many people use free will as complete liberty by the individual to choose and perform any action that has been chosen. This is not true in our personal experience and it is not true in Bible teaching. Why, therefore, should it be accepted as absolute Bible doctrine?   I can choose to accept Christ and I can choose to obey Him because He enables me to do so. Free will has two applications to us. First, I have a certain limited free will in earthly decisions. I can choose chocolate ice cream instead of vanilla. I can choose to ask God for His help in a particular matter. Though this free will is very limited, our small minds assume it to be larger than it is because of the seemingly infinite varieties of earthly actions we can choose to make. But we are much more limited than most people understand. I cannot will to fly or to be President of the United States or to refuse to think a wrong thought all day and expect to be successful. Free will has serious limitations.   Second, I have the free will to reject the working of God in my heart. That is, God (of His own choice) does not remove my ability to say "no" to the wooing of His Holy Spirit. Therefore, although Christ has promised to draw all men to Him through the cross (John 12:32And I, if I be lifted up from the earth, will draw all men unto me.
See All...), He does not force me to accept His call. As Christ told Jerusalem and the people in it, "how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not!" (Matthew 23:37O Jerusalem, Jerusalem, thou that killest the prophets, and stonest them which are sent unto thee, how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not!
See All...). The word "would" is a form of "willing." He was willing to gather them, but they were not willing and therefore they were lost. There is no irresistible grace here. However, there is no absolute "free will" either. No doubt, they needed Him to be willing before they could be willing.   As to your question about salvation, free will is not a right someone has to lose their salvation. We cannot will ourselves new parents. When in heaven, we will not be able to will ourselves out of heaven. If we are saved, we have become members of the body, flesh, and bones of Jesus Christ (Ephesians 5:30For we are members of his body, of his flesh, and of his bones.
See All...). This is not simply a condition that we can reverse by an act of the will.   We have elevated the "decision" too much in salvation. I am not denying that we decide to accept the offer of salvation. But this is not what saves us. Our salvation is all of God and all our decision does is allow God to apply His redemption to our souls. We spend too much time thinking about what we did. Salvation is of the Lord! (See Jonah 2:10And the LORD spake unto the fish, and it vomited out Jonah upon the dry land.
See All...). I had no "right" to be saved. I simply trusted in what Christ did for me. He called and I responded to His enabling power. I did not will myself in and I cannot will myself out.