He that covereth his sins shall not prosper: but whoso confesseth and forsaketh them shall have mercy. Proverbs 28:13
"the goodness of God leadeth thee to repentance" Romans 2:4
We are talking about Christians here, who have already repented when they got born again. Some people think that we never need to repent after being born again because all of our sins are forgiven past, present, and future. It is true that Christ died for all your sins: past, present, and future; however, it is not true that you need not repent when you sin after you accept Christ.
Is any sick among you? let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord: 15 And the prayer of faith shall save the sick, and the Lord shall raise him up; and if he have committed sins, they shall be forgiven him. 16 Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much. James 5:14-16
Notice this verse was written directly to Christians, and more specifically, to a Christian who is sick. Not only should that person have the elders to pray for them, but they should repent of their sins, which will be forgiven.
Another verse written to Christians is I John 1:9 which says, "If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness." Obviously, this verse says we should confess our sins and that He will forgive us of our sins. I want to point out that Jesus said we should forgive a person seven times in a day, if they sinned against us seven times. So, we can expect Jesus to forgive us seven times in one day as well. What a loving Savior we have! He forgives us every time! Praise the Lord!
The third and final example I'll give is in I Corinthians 5, where Paul points out a couple that needs to repent and stop sinning or be kicked out of the church. Thankfully, we see in II Corinthians 7:9 that this couple did stop sinning, and Paul rejoiced that they "sorrowed to repentance". So, again, we see that Christians need to repent when they sin.
Someone might ask, "If I'm already forgiven, why do I need to repent?" When you first got saved, did Christ die at that moment? Of course not. He died for you a couple thousand years ago, but you received your salvation at that moment.
The same idea is true with repentance for any sins you've committed. You have already been forgiven, but you need to receive that forgiveness. We read above that the Holy Spirit through James, Peter, and Paul wrote that Christians must confess their sins and repent, so they can receive forgiveness. Forgiveness needs to be received, just like salvation needs to be received.