As Paul says,
"For I am confident of this very thing, that He who began a good work in you will perfect it until the day of Christ Jesus."
"In Him, you also, after listening to the message of truth, the gospel of your salvation-- having also believed, you were sealed in Him with the Holy Spirit of promise, who is given as a pledge of our inheritance, with a view to the redemption of God's own possession, to the praise of His glory."
Salvation is not an act of man.. It is act of God.. We all know the thief had real faith.. because Jesus said it! It he did not die there, I am sure he would have lived a life pleasing to Lord.. Above scriptures (and many more) support this..
Salvation is an act of God -- no question. It is only through Him that we are saved. But it is man's choice whether they choose to accept His saving grace or not. God has granted us free will to either follow Him or go wrong.