I once doubted the death, burial, and resurrection part of my baptism. I have cleared my conscience on that part. I came to realize that I knew what I was doing on that part. For some reason, I have started doubting my repentance before baptism. I knew before I was immersed that I had to change my manner of life after I was baptized. I decided that I was going to do my best to change and live my life for the Lord. For some reason, I am doubting. It seems as though I thought the change occurred after baptism. I thought repentance before baptism was the decision to change my life after I became a Christian. In other words, I decided that I was going to change. Isn't it the decision to change that occurs before baptism and the actual change that occurs after baptism? Do you follow what I'm saying?
Repentance means a change in the direction you are heading. "Therefore, King Agrippa, I was not disobedient to the heavenly vision, but declared first to those in Damascus and in Jerusalem, and throughout all the region of Judea, and then to the Gentiles, that they should repent, turn to God, and do works befitting repentance" (Acts 26:19-20). One repents and then begins obeying God, thus doing actions that are in accordance with the repentance. The actions are not the repentance, but the result of repentance. The actions are not a one time deed but are a new way of life. One of the earliest demonstrations of a change in behavior is shown by submitting to baptism to become a Christian. It is a declaration that you started walking a new path. "Therefore we were buried with Him through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life" (Romans 6:4).
You can see the repentance illustrated in the person's attitude. "For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death. For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter" (II Corinthians 7:10-11). A person who has repented doesn't leave things as they are, thinking that God is going to accept them anyway. The repentant person makes major course corrections in his life.
The fact that a person has repented does not imply that he will not make the same mistakes again. A person sometimes has to learn how to avoid the traps of sin. "And if he sins against you seven times in a day, and seven times in a day returns to you, saying, 'I repent,' you shall forgive him" (Luke 17:4). The key is that the person is working against sin and is no longer content to just let it slide.
Nor does it mean that a person who has repented will not make other mistakes. "If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. If we say that we have not sinned, we make Him a liar, and His word is not in us" (I John 1:8-10). There will be sins we must address in our life which need to be repented of and corrections made in how we live. But the fact that we slip does not negate the fact that we repented earlier in our life when we became a Christian.
Doubts about what you've done in the past are not productive. As James warns, "for he who doubts is like a wave of the sea driven and tossed by the wind" (James 1:6). Doubt undermines your faith and a lack of faith is sin, "for whatever is not from faith is sin" (Romans 14:23). The problem is not whether you were saved because that did take place and was properly done. The problem is that you've allowed Satan to your faith in God's power to save you.