Fruitful faith has a target or object upon which it is founded. It varies, but it could be reason, experience or a person, among other things. It's why we get our word faithful from faith: a faithful person has demonstrated two things: they have the ability to produce (you believe they can do a thing) and they will produce (you trust that they will do as they say). Faith placed in a faithful person always carries an expectation of experience. Such faith is well founded or well grounded because the person has demonstrated themselves to be reliable.
Therefore, faith is not demonstrated by how you feel, it's not demonstrated by the beliefs you hold, neither the doctrines you keep.
Faith is demonstrated by what is produced: the outcome, the experience. Faith "is the assurance of things hoped for, the conviction of things not seen. For by it the men of old gained approval." What happens when the thing not seen and hoped for, shows up? Faith moves out of the way and gives place to the experience.
Therefore, believing a doctrine for the sake of belief only, is worthless. That is not faith because such belief produces no work, no experience. James summed it up by suggesting that the demons have a proper belief too, but it is to them, worthless.
“But someone may well say, "You have faith and I have works; show me your faith without the works, and I will show you my faith by my works."
You believe that God is one. You do well; the demons also believe, and shudder.
But are you willing to recognize, you foolish fellow, that faith without works is useless?” (James 2:18-19)Therefore, the conviction of the thing unseen must always bring fruit. You can know if your faith was well place by observing the fruit. As a matter of fact, you can determine the efficacy of a work or ministry by the same standard - "you shall know them by their fruit" (Matthew 7:20)
But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control; against such things there is no law. (Hebrews 11:1)
But the wisdom from above is first pure, then peaceable, gentle, reasonable, full of mercy and good fruits, unwavering, without hypocrisy. And the seed whose fruit is righteousness is sown in peace by those who make peace. (James 3:17-18)