What follows is a response to a penitent's concern that their remaining sense of guilt for past sins should prohibit them from submitting to Christian Baptism as they understood 1 Peter 3:8.
I am glad you are approaching this sacred responsibility with care and study. The point the Apostle is making says that baptism, when it is properly a symbol of the putting away of sin, and of the renewing influences of the Holy Spirit, and an act of unreserved dedication to God—now saves us. In that light the “pledge” prior to baptism is not to be confused with the promise received after baptism. The pledge is in your court – that you pledge your intent in coming to the sacrament of baptism is that you are wholly committed to giving your life, past, present and future, to Christ.
The issue of guilt is separate from “clear conscience” in that guilt is the sense of shame God gives to tell of wrong doing and conscience is the tool used by the Holy Spirit to communicate that shame. Guilt is useful when it is prodding us to repentance and right action. Guilt is harmful when oppressing us and bringing give up hope in our ability to right the wrongs we have caused. However, guilt is a wonderful gift that keeps reminding us that God’s forgiveness has freed us from the penalty and power of sin while at the same time prodding us to do the work the of repentance in setting right what we have wronged to the extent we are able.
It is in baptism we receive the internal presence of the Holy Spirit which gives us the strength to do all the above – something we are not otherwise capable. See Acts 2:38 , “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.”
One final thing about sin and guilt. When God forgives you are forgiven – however – our personal sense of forgiveness takes time for two reasons. The first has to do with the fallout of our sin – the people we hurt and the damage done still has to be righted to the extent possible. The second is like a wound that continues to hurt or itch long after it is healed – we have to accept the wound is healed even though we still feel the pain or itch left behind.