Romans 8:11

"There is therefore now no condemnation to those who are in Christ Jesus, who do not walk according to the flesh, but to the Spirit"

When we are troubled by guilt or regret we should recognize that we can change. We can confess our struggles to God in prayer and ask for forgiveness. When we do, God will forgive us completely without reservation. Then we can forgive ourselves just as God has forgiven us: thoroughly and unconditionally.