I thank God for my faith, it's all up to me from here. For me, I found this out from the Bible. The scriptures tell me that when I was saved, God gave me a share of faith. I don't produce it, He gives it to me freely! But, from there, it is up to me to grow it through reading and hearing the word of God. No one ever preached this, no one told me and I am 72 years old! The way I learned was , after God gave me the thirst, the Bible told me.
it's all there, read it yourself!
Some one said it is "Human is to error!"...I say, it is very human to doubt and nothing in this life of ours is more erroneous than doubt. GOD is the epitome of truth and being positive.
I am saved, I have faith and I sin in many ways, and one of them is doubt about all of this. Like the old slave hymn, "Amazing Grace", when the devil and doubt creep in, I just go back to the day I was first saved and my faith and belief flood in , satin and doubt vanish...thanks be to God!