Continue in My word - John 8

John 8:31-32" ... If you continue in My word, then you are truly disciples of Mine; and you will know the truth, and the truth will make you free."

It's like we get dirty and get into a shower. The dirt are the lies of the enemy, of this world. There's no point dabbing a little bit of water here and there. We are to be completely exposed in the shower, and continue in the running water, then the water will gradually wash away all the doubts and unbelief, and we will know the truth.
We need to continue to be exposed to God's living word, to be exposed to the truth, until His word becomes such a reality, until all the doubts are gone.
Faith comes from hearing, and hearing word of God. If we continue to hear God's word, then our faith will grow. And perfect love cast out fear. When we're in the shower of truth and faith long enough, we'll be clean of the dirt of doubt and unbelief. And when the faith is perfect, we'll be set free.