If you consider yourself a Christian, and that you made a free-will decision to have faith in God...
Think of a person you know who has heard the same Gospel you have but has rejected it...
Assuming that making a decision to believe in Christ is a better one than rejecting Him, what about you allowed you to make that better decision? It had to be something about you that caused you to choose that way. And it had to be something better than the person choosing against. Was it your better intelligence? Your better analytic capabilities? Your better ability to understand things, even though you both heard the same gospel message? Something had to be better about you...what was it?
That's why the Bible declares that God's sovereign will is the cause of the gracious gifts of faith and belief in Him, not a person's "free will" -- lest any man should boast (of himself over the glory that is only due God):
John 1:12-13 - "12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: 13 Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God."
John 6:29 - "Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent."
John 6:44 - "No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day."
John 6:65 - "And he said, Therefore said I unto you, that no man can come unto me, except it were given unto him of my Father."
Eph 2:8-9 - "8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast."
Phil 1:29 – "For unto you it is given in the behalf of Christ, not only to believe on him, but also to suffer for his sake;"
Jam 1:18 – "Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures."