This post will probably be most understood by readers who have an affiliation with the CoC, because faith is something that is extremely understressed there. Understanding what faith itself is was a big step for me, because in the CoC we do not rely much on faith. We try to prove everything, and we really deep down believe that everything can be shown from the Bible, and so there's no need for faith because it can all be argued and explained rationally (so they say).
Often, what happens when someone from the CoC decides to leave, is that since all their faith was really in the "scriptural evidence" rather than God, when that scriptural evidence falls to pieces, their faith falls to pieces. (It goes without saying that there are always exceptions, this is just a general observation.) There are others, though, who are fortunate to somehow hold onto that thread of faith in God, and have to sort out where to go from there.
True faith is a God-given gift. It is one of the three theological virtues (faith, hope, love) which we cannot fabricate of our own accord, they must be given to us by God. And so, our reason takes us to a point, we see the reasonable arguments for the Church, but there comes a time when we must finally rest on faith, especially if there are lingering doubts. This is a hard thing to do for ex-CoCers! It is so pounded into us that any doubt is BAD BAD BAD that we're afraid of joining up anywhere unless we're absolutely 100% sure. If there are any doubts at all, it feels like we're in limbo, not able to go back but not able to move forward either.
What is important to realize is the distinction between voluntary doubt and involuntary doubt. Here's something from Catholic answers on that:
Obstinate doubt is a person’s refusal to give assent to something and persistance in this refusal through his own fault. It is important to distinguish this willful refusal to assent from merely having hesitancy or conflicted feelings about something that one accepts.
Doubt is distinguished as either voluntary or involuntary. The Catechism explains:
Voluntary doubt about the faith disregards or refuses to hold as true what God has revealed and the Church proposes for belief. Involuntary doubt refers to hesitation in believing, difficulty in overcoming objections connected with the faith, or also anxiety aroused by its obscurity. If deliberately cultivated, doubt can lead to spiritual blindness (CCC 2088).
Involuntary doubt is not sinful and may be experienced by any sincere believer. Voluntary doubt, on the other hand, is grave issue.
When doubts arise, we must rely on faith. Now, that statement kind of sounds obvious, but think about this...if we are expecting to understand everything and rid ourselves of all lingering doubts before we do anything, would we really have faith then? Or would we just be counting on our intelligence and reason alone to get us through? This kind of outlook could result in a very weak faith ultimately, so that if someone who converted in this way one day came across a teaching that they couldn't understand intellectually, it might cause a loss of whatever little faith they had to begin with, because they haven't been really relying on faith, just as those who relied so heavily on scriptural evidence can see their faith in God dashed as the evidence for their scriptural interpretation is dashed.
All this to say, the fact that we may have lingering doubts about some things the Church teaches is absolutely normal, and in fact is good practice for relying on faith! Remember that faith is not something that comes from us, it comes from God, and so we need to be sure to pray for faith. God knows we need it, be He also wants to see that we acknowledge that we need it, and that we know we can only receive it from Him.
A few months ago at mass, a reading from Luke was read, and my husband made a comment about different ways it could be read. Read this passage, and think of the blind man, not as physically blind, but as spiritually blind, as not being able to see the truth clearly, but wanting to.
And it came to pass, that as he was come nigh unto Jericho, a certain blind man sat by the way side begging:
And hearing the multitude pass by, he asked what it meant. And they told him, that Jesus of Nazareth passeth by. And he cried, saying, Jesus, thou son of David, have mercy on me. And they which went before rebuked him, that he should hold his peace: but he cried so much the more, Thou son of David, have mercy on me.
And Jesus stood, and commanded him to be brought unto him: and when he was come near, he asked him, Saying, What wilt thou that I shall do unto thee? And he said, Lord, that I may receive my sight. And Jesus said unto him, Receive thy sight: thy faith hath saved thee.
And immediately he received his sight, and followed him, glorifying God: and all the people, when they saw it, gave praise unto God.
Gives a whole new meaning to it doesn't it? For those struggling with doubt, remember this prayer, and say it often. "Lord, I believe, help my unbelief." Ask for faith, and you will receive.