Can a person firmly believe in eternal security, that once saved, always saved, but still struggle with spiritual doubt about the security of their salvation? I think so. Actually I know so.
I have counseled many who believe with all their heart that Jesus will not lose any that the Father has given him (John 17). That Jesus holds each born-again believer in the palm of his hand and will never let go. They believe that once their names are written in the Lamb’s book of life, they are there to stay.
But they still struggle with lagging spiritual doubt. Was I really saved? Did I do everything that I was supposed to do: repent, confess, admit, believe, receive? Did I pray the right things? Did it really take effect? Am I in?
It appears to me that if a person is truly asking questions about their spiritual condition with a sincere and honest heart, God has probably saved them or is about to. In other words, the transaction has taken place. A sensitivity to the things of God are evidence of salvation.
1 Corinthians 2:13-14 And we impart this in words not taught by human wisdom but taught by the Spirit, interpreting spiritual truths to those who are spiritual. The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
If there is no evidence of spiritual discernment, there is a problem. If there are no fruits of the Spirit (Gal. 5) that is a serious issue. If the person can not understand any spiritual truth and is more natural than spiritual, then the transformation probably hasn’t happened.
But lagging spiritual doubt might be a good thing in that it demonstrates a true yearning and sensitivity to the things of God, which might be the greatest demonstration of true salvation.